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2012

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Articles 481 - 510 of 841

Full-Text Articles in Mathematics

Solution Of Problem 947, Eugen J. Ionascu Jan 2012

Solution Of Problem 947, Eugen J. Ionascu

Faculty Bibliography

No abstract provided.

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Weight: Does It Really Matter?, Jennifer Brown Jan 2012

Weight: Does It Really Matter?, Jennifer Brown

Faculty Bibliography

Differential weighting promises to improve the validity of a measure. This study examines whether similar results would be found using weighted, unweighted and standardized z scores from the All Stars Core survey. It was concluded that the weighted systems were developed to equate the questions within the scales and to ease the process for customers without access to data analysis programs; however, the standardized scores were the more appropriate method for equating the test items.

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A Generalized Birkhoff-Rott Equation For Two-Dimensional Active Scalar Problems, Hui Sun, David Uminsky, Andrea L. Bertozzi Jan 2012

A Generalized Birkhoff-Rott Equation For Two-Dimensional Active Scalar Problems, Hui Sun, David Uminsky, Andrea L. Bertozzi

Mathematics

In this paper we derive evolution equations for the two-dimensional active scalar problem when the solution is supported on one-dimensional curves. These equations are a generalization of the Birkhoff–Rott equation when vorticity is the active scalar. The formulation is Lagrangian and it is valid for nonlocal kernels K that may include both a gradient and an incompressible term. We develop a numerical method for implementing the model which achieves second order convergence in space and fourth order in time. We verify the model by simulating classic active scalar problems such as the vortex sheet problem (in the case of inviscid, …

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Network-Based Criterion For The Success Of Cooperation In An Evolutionary Prisoner's Dilemma, Stephen Devlin, T Treloar Jan 2012

Network-Based Criterion For The Success Of Cooperation In An Evolutionary Prisoner's Dilemma, Stephen Devlin, T Treloar

Mathematics

We consider an evolutionary prisoner's dilemma on a random network. We introduce a simple quantitative network-based parameter and show that it effectively predicts the success of cooperation in simulations on the network. The criterion is shown to be accurate on a variety of networks with degree distributions ranging from regular to Poisson to scale free. The parameter allows for comparisons of random networks regardless of their underlying topology. Finally, we draw analogies between the criterion for the success of cooperation introduced here and existing criteria in other contexts.

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Convergence And Energy Landscape For Cheeger Cut Clustering, X Bresson, T Laurent, David Uminsky, J Von Brecht Jan 2012

Convergence And Energy Landscape For Cheeger Cut Clustering, X Bresson, T Laurent, David Uminsky, J Von Brecht

Mathematics

This paper provides both theoretical and algorithmic results for the l 1-relaxation of the Cheeger cut problem. The l2- relaxation, known as spectral clustering, only loosely relates to the Cheeger cut; however, it is convex and leads to a simple optimization problem. The l1-relaxation, in contrast, is non-convex but is provably equivalent to the original problem. The l1-relaxation therefore trades convexity for exactness, yielding improved clustering results at the cost of a more challenging optimization. The first challenge is understanding convergence of algorithms. This paper provides the first complete proof of convergence for …

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Model Reduction Of Linear Pde Systems: A Continuous Time Eigensystem Realization Algorithm, John R. Singler Jan 2012

Model Reduction Of Linear Pde Systems: A Continuous Time Eigensystem Realization Algorithm, John R. Singler

Mathematics and Statistics Faculty Research & Creative Works

The Eigensystem Realization Algorithm (ERA) is a well known system identification and model reduction algorithm for discrete time systems. Recently, Ma, Ahuja, and Rowley (Theoret. Comput. Fluid Dyn. 25(1) : 233-247, 2011) showed that ERA is theoretically equivalent to the balanced POD algorithm for model reduction of discrete time systems. We propose an ERA for model reduction of continuous time linear partial differential equation systems. The algorithm differs from other existing approaches as it is based on a direct approximation of the Hankel integral operator of the system. We show that the algorithm produces accurate balanced reduced order models for …

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Mathematical Modeling And Simulation Of Biologically Inspired Hair Receptor Arrays In Laminar Unsteady Flow Separation, John R. Singler, Belinda A. Batten, Benjamin T. Dickinson Jan 2012

Mathematical Modeling And Simulation Of Biologically Inspired Hair Receptor Arrays In Laminar Unsteady Flow Separation, John R. Singler, Belinda A. Batten, Benjamin T. Dickinson

Mathematics and Statistics Faculty Research & Creative Works

Bats possess arrays of distributed flow-sensitive hair-like mechanoreceptors on their dorsal and ventral wing surfaces. Bat wing hair receptors are known to play a significant role in flight maneuverability and are directionally most sensitive to reversed flow over the wing. in this work, we consider the mechanics of flexible hair-like structures for the time accurate detection and visualization of hydrodynamic images associated with unsteady near surface flow phenomena. a nonlinear viscoelastic model of a hair-like structure coupled to an unsteady nonuniform flow is proposed. Writing the hair model in nondimensional form, we identify five dimensionless groups that govern hair behavior. …

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A Linear Energy Stable Scheme For A Thin Film Model Without Slope Selection, Wenbin Chen, Sidafa Conde, Cheng Wang, Xiaoming Wang, Steven M. Wise Jan 2012

A Linear Energy Stable Scheme For A Thin Film Model Without Slope Selection, Wenbin Chen, Sidafa Conde, Cheng Wang, Xiaoming Wang, Steven M. Wise

Mathematics and Statistics Faculty Research & Creative Works

We present a linear numerical scheme for a model of epitaxial thin film growth without slope selection. the PDE, which is a nonlinear, fourth-order parabolic equation, is the L2 gradient flow of the energy ∫Ω(-1/2 ln(1 + |ø|2) + ε2 2 |Ø(x)|2) dx. the idea of convex-concave decomposition of the energy functional is applied, which results in a numerical scheme that is unconditionally energy stable, i.e., energy dissipative. the particular decomposition used here places the nonlinear term in the concave part of the energy, in contrast to a previous convexity splitting scheme. as a result, the numerical scheme is fully …

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Productivity Formulae Of An Infinite-Conductivity Hydraulically Fractured Well Producing At Constant Wellbore Pressure Based On Numerical Solutions Of A Weakly Singular Integral Equation Of The First Kind, Chaolang Hu, Jing Lu, Xiaoming He Jan 2012

Productivity Formulae Of An Infinite-Conductivity Hydraulically Fractured Well Producing At Constant Wellbore Pressure Based On Numerical Solutions Of A Weakly Singular Integral Equation Of The First Kind, Chaolang Hu, Jing Lu, Xiaoming He

Mathematics and Statistics Faculty Research & Creative Works

In order to increase productivity, it is important to study the performance of a hydraulically fractured well producing at constant wellbore pressure. This paper constructs a new productivity formula, which is obtained by solving a weakly singular integral equation of the first kind, for an infinite-conductivity hydraulically fractured well producing at constant pressure. And the two key components of this paper are a weakly singular integral equation of the first kind and a steady-state productivity formula. A new midrectangle algorithm and a Galerkin method are presented in order to solve the weakly singular integral equation. The numerical results of these …

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Almost Oscillatory Three Dimensional Dynamic Systems, Elvan Akin, Zuzana Dosla, Bonita Lawrence Jan 2012

Almost Oscillatory Three Dimensional Dynamic Systems, Elvan Akin, Zuzana Dosla, Bonita Lawrence

Mathematics and Statistics Faculty Research & Creative Works

In this article, we investigate oscillation and asymptotic properties for 3D systems of dynamic equations. We show the role of nonlinearities and we apply our results to the adjoint dynamic systems.

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S-Index: A Comprehensive Scholar Impact Index, Shlomo S. Sawilowsky Jan 2012

S-Index: A Comprehensive Scholar Impact Index, Shlomo S. Sawilowsky

Theoretical and Behavioral Foundations of Education Faculty Publications

Limitations of impact indices to compare scholars across disciplines and time based only the number of publications and citations are discussed. The S-index, based on more comprehensive scholar impact factors, is proposed.

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A Note On Hopfian And Co-Hopfian Abelian Groups, Brendan Goldsmith, Ketao Gong Jan 2012

A Note On Hopfian And Co-Hopfian Abelian Groups, Brendan Goldsmith, Ketao Gong

Conference papers

The notions of Hopfian and co-Hopfian groups have been of interest for some time. In this present work we exploit some unpublished ideas of Corner to answer questions relating to such groups. In particular, we extend an answer given by Corner to a problem of Beaumont and Pierce and show how the properties may be lifted from subgroups to the whole group in certain situations.

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Cubes In {0,1, ...N}³, Eugen J. Ionascu, Rodrigo Obando Jan 2012

Cubes In {0,1, ...N}³, Eugen J. Ionascu, Rodrigo Obando

Faculty Bibliography

The main aim of this paper is to describe a procedure for calculating the number of cubes that have coordinates in the set {0, 1, . . . , n}. For this purpose we continue and, at the same time, revise some of the work begun in a sequence of papers about equilateral triangles and regular tetrahedra all having integer coordinates for their vertices. We adapt the code that was included in a paper by the first author and was used to calculate the number of regular tetrahedra with vertices in {0, 1, . . . , n}3. The idea …

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On The Logic Of Reverse Mathematics, Alaeddine Saadaoui Jan 2012

On The Logic Of Reverse Mathematics, Alaeddine Saadaoui

Theses, Dissertations and Capstones

The goal of reverse mathematics is to study the implication and non-implication relationships between theorems. These relationships have their own internal logic, allowing some implications and non-implications to be derived directly from others. The goal of this thesis is to characterize this logic in order to capture the relationships between specific mathematical works. The results of our study are a finite set of rules for this logic and the corresponding soundness and completeness theorems. We also compare our logic with modal logic and strict implication logic. In addition, we explain two applications of S-logic in topology and second order arithmetic.

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A Study Of The Gam Approach To Solve Laminar Boundary Layer Equations In The Presence Of A Wedge, Rahmat Ali Khan, Muhammad Usman Jan 2012

A Study Of The Gam Approach To Solve Laminar Boundary Layer Equations In The Presence Of A Wedge, Rahmat Ali Khan, Muhammad Usman

Mathematics Faculty Publications

We apply an easy and simple technique, the generalized ap- proximation method (GAM) to investigate the temperature field associated with the Falkner-Skan boundary-layer problem. The nonlinear partial differ- ential equations are transformed to nonlinear ordinary differential equations using the similarity transformations. An iterative scheme for the non-linear ordinary differential equations associated with the velocity and temperature profiles are developed via GAM. Numerical results for the dimensionless ve- locity and temperature profiles of the wedge flow are presented graphically for different values of the wedge angle and Prandtl number.

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From Conic Intersections To Toric Intersections: The Case Of The Isoptic Curves Of An Ellipse, Thierry Dana-Picard, Nurit Zehavi, Giora Mann Jan 2012

From Conic Intersections To Toric Intersections: The Case Of The Isoptic Curves Of An Ellipse, Thierry Dana-Picard, Nurit Zehavi, Giora Mann

The Mathematics Enthusiast

Starting from the study of the orthoptic curves of parabolas and ellipses, we generalize to the case of isoptic curves for any angle, i.e. the geometric locus of points from which a parabola or an ellipse are viewed under a given angle. This leads to the investigation of spiric curves and to the construction of these curves as an actual intersection of a self-intersecting torus with a plane. The usage of a Computer Algebra System facilitated this investigation.

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Student Enrolment In Classes With Frequent Mathematical Discussion And Its Longitudinal Effect On Mathematics Achievement, Karl W. Kosko Jan 2012

Student Enrolment In Classes With Frequent Mathematical Discussion And Its Longitudinal Effect On Mathematics Achievement, Karl W. Kosko

The Mathematics Enthusiast

Mathematical discussion has been identified as being beneficial to students’ understandings of mathematics (Goos, 1995; Lee, 2006). Students in classrooms with more effective math discussion have been observed to engage more frequently in discussion (e.g. Hiebert & Wearne, 1993), but the converse is not necessarily true (e.g. Manouchehri & St. John, 2006). Utilizing hierarchical linear modeling, the present study examined student enrollment in classes with more and less frequent discussion and such enrollment’s effect on mathematics achievement over time. Results indicated that students enrolled in classes that discuss math “almost every day” consistently have higher math achievement than students enrolled …

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Improved Left Ventricular Mass Quantification With Partial Voxel Interpolation – In-Vivo And Necropsy Validation Of A Novel Cardiac Mri Segmentation Algorithm, Noel C.F. Codella, Hae Yeoun Lee, David S. Fieno, Debbie W. Chen, Sandra M. Hurtado Rua, Minisha Kochar, John Paul Finn, Robert Judd, Parag Goyal, Jesse Schenendorf, Matthew D. Cham, Richard B. Devereux, Martin Prince, Yi Wang, Jonathan W. Weinsaft Jan 2012

Improved Left Ventricular Mass Quantification With Partial Voxel Interpolation – In-Vivo And Necropsy Validation Of A Novel Cardiac Mri Segmentation Algorithm, Noel C.F. Codella, Hae Yeoun Lee, David S. Fieno, Debbie W. Chen, Sandra M. Hurtado Rua, Minisha Kochar, John Paul Finn, Robert Judd, Parag Goyal, Jesse Schenendorf, Matthew D. Cham, Richard B. Devereux, Martin Prince, Yi Wang, Jonathan W. Weinsaft

Mathematics and Statistics Faculty Publications

Background—CMR typically quantifies LV mass (LVM) via manual planimetry (MP), but this approach is time consuming and does not account for partial voxel components - myocardium admixed with blood in a single voxel. Automated segmentation (AS) can account for partial voxels, but this has not been used for LVM quantification. This study used automated CMR segmentation to test the influence of partial voxels on quantification of LVM. Methods and Results—LVM was quantified by AS and MP in 126 consecutive patients and 10 laboratory animals undergoing CMR. AS yielded both partial voxel (ASPV) and full voxel (ASFV) …

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The Secretary Problem From The Applicant's Point Of View, Darren B. Glass Jan 2012

The Secretary Problem From The Applicant's Point Of View, Darren B. Glass

Math Faculty Publications

Searching for a job is always stressful and, with unemployment rates at their highest levels in years, never more so than now. Applicants can and should use every advantage at their disposal to obtain a job which is rewarding, financially and otherwise. While this author believes a math major gives applicants many advantages as they search for their dream job, one often overlooked is the ability to strategize and schedule their interviews to maximize the chance of landing that job.

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Mathematical Competitions In Hungary: Promoting A Tradition Of Excellence & Creativity, Julianna Connelly Stockton Jan 2012

Mathematical Competitions In Hungary: Promoting A Tradition Of Excellence & Creativity, Julianna Connelly Stockton

The Mathematics Enthusiast

Hungary has long been known for its outstanding production of mathematical talent. Extracurricular programs such as camps and competitions form a strong foundation within the Hungarian tradition. New types of competitions in recent years include team competitions, multiple choice competitions, and some exclusively for students who are not in a special mathematics class. This study explores some of the recent developments in Hungarian mathematics competitions and the potential implications these changes have for the very competition-driven system that currently exists. The founding of so many new competitions reflects a possible shift in the focus and purpose of competitions away from …

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Some Reflections On Mathematics And Mathematicians: Simple Questions, Complex Answers, Juan Eduardo Nápoles Valdes Jan 2012

Some Reflections On Mathematics And Mathematicians: Simple Questions, Complex Answers, Juan Eduardo Nápoles Valdes

The Mathematics Enthusiast

In this work we present some reflections on mathematics and mathematicians. Special emphasis is placed on the questions (1) what is mathematics? And (2) what is a mathematician? Some reflections and open questions are posed at the end of the work.

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What Does It Take To Teach Nonmajors Effectively?, Feryal Alayont, Gizem Karaali, Lerna Pehlivan Jan 2012

What Does It Take To Teach Nonmajors Effectively?, Feryal Alayont, Gizem Karaali, Lerna Pehlivan

Pomona Faculty Publications and Research

Most MAA members teach mathematics at the college level, and many often teach courses intended for nonmajors. Indeed this is one of the main responsibilities of a mathematics department: offering service courses for client departments and general education courses for nonmajors. The three of us have been thinking about the question of how to teach nonmajors successfully for a while now. Finally we decided on a time-tested method of figuring things out: if you don't know what to do, ask the experts. We organized a panel titled "Effective Strategies for Teaching Classes for Nonmajors" for MAA MathFest 2012 and invited …

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Unitary Equivalence To A Truncated Toeplitz Operator: Analytic Symbols, Stephan Ramon Garcia, Daniel E. Poore '11, William T. Ross Jan 2012

Unitary Equivalence To A Truncated Toeplitz Operator: Analytic Symbols, Stephan Ramon Garcia, Daniel E. Poore '11, William T. Ross

Pomona Faculty Publications and Research

Unlike Toeplitz operators on H², truncated Toeplitz operators do not have a natural matricial characterization. Consequently, these operators are difficult to study numerically. In this paper we provide criteria for a matrix with distinct eigenvalues to be unitarily equivalent to a truncated Toeplitz operator having an analytic symbol. This test is constructive, and we illustrate it with several examples. As a byproduct, we also prove that every complex symmetric operator on a Hilbert space of dimension ≤ 3 is unitarily equivalent to a direct sum of truncated Toeplitz operators.

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Changes Across 25 Years Of Statistics In Medicine, Johanna S. Hardin Jan 2012

Changes Across 25 Years Of Statistics In Medicine, Johanna S. Hardin

Pomona Faculty Publications and Research

[This piece is a series of interviews with giants in the field of medicine on their views of how statistics is changing medicine. I interviewed the editor of the New England Journal of Medicine, a preeminent doctor/researcher of lung cancer, the director of the LA County Department of Public Health, and a Harvard statistician who sits on the editorial board of the New England Journal of Medicine.]

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Second Gradient Viscoelastic Fluids: Dissipation Principle And Free Energies, G. Amendola, M. Fabrizio, John Murrough Golden Jan 2012

Second Gradient Viscoelastic Fluids: Dissipation Principle And Free Energies, G. Amendola, M. Fabrizio, John Murrough Golden

Articles

We consider a generalization of the constitutive equation for an incompressible second order fluid, by including thermal and viscoelastic effects in the expression for the stress tensor. The presence of the histories of the strain rate tensor and its gradient yields a non-simple material, for which the laws of thermodynamics assume a modified form. These laws are expressed in terms of the internal mechanical power which is evaluated, using the dynamical equation for the fluid. Generalized thermodynamic constraints on the constitutive equation are presented. The required properties of free energy functionals are discussed. In particular, it is shown that they …

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On Super And Hereditarily Hopfian And Co-Hopfian Abelian Groups, Brendan Goldsmith, Katao Kong Jan 2012

On Super And Hereditarily Hopfian And Co-Hopfian Abelian Groups, Brendan Goldsmith, Katao Kong

Articles

The notions of Hopfian and co-Hopfian groups have been of interest for some time. In this present work we characterize the more restricted classes of hereditarily Hopfian (co-Hopfian) and super Hopfian (co-Hopfian) groups in the case where the groups are Abelian.

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Medicine, Statistics, And Education: The Inextricable Link, Katharine K. Brieger '11, Johanna S. Hardin Jan 2012

Medicine, Statistics, And Education: The Inextricable Link, Katharine K. Brieger '11, Johanna S. Hardin

Pomona Faculty Publications and Research

No abstract provided.

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An Investigation Of Air Resistance On Projectile Motion From Aristotle To Euler, Michael Edward Clayton Jan 2012

An Investigation Of Air Resistance On Projectile Motion From Aristotle To Euler, Michael Edward Clayton

Theses Digitization Project

From antiquity until today, mathematicians have tried to develop a theory of projectile motion. The development of a theory of projectile motion began with just a basic observation of motion by the great Greek mathematician Aristotle and has evolved to become more than conjecture or hypothesis, but a well developed science of prediciting the flight and accuracy of a projectile in motion. This thesis traces the development of the theory of projectile motion from Greek antiquity to about the mid 1700's.

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Closure Operations In Commutative Rings, Chloette Joy Samsam Jan 2012

Closure Operations In Commutative Rings, Chloette Joy Samsam

Theses Digitization Project

The purpose of this study is to survey different types of closures and closure operations on commutative rings and ideals.

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Orthogonal Polynomials, George Gevork Antashyan Jan 2012

Orthogonal Polynomials, George Gevork Antashyan

Theses Digitization Project

This thesis will show work on Orthogonal Polynomials. In mathematics, the type of polynomials that are orthogonal to each other under inner product are called orthogonal polynomials. Jacobi polynomials, Laguerre polynomials, and Hermite polynomials are examples of classical orthogonal polynomials that was invented in the nineteenth century. The theory of rational approximations is one of the most important applications of orthogonal polynomials.

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