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2003

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Articles 31 - 60 of 269

Full-Text Articles in Mathematics

Invertibility Of Current Density From Near-Field Electromagnetic Data, Evangelos A. Coutsias, Daniel Sheltraw Sep 2003

Invertibility Of Current Density From Near-Field Electromagnetic Data, Evangelos A. Coutsias, Daniel Sheltraw

Branch Mathematics and Statistics Faculty and Staff Publications

The problem of determining a current density confined to a volume from measurements of the magnetic and electric fields it produces exterior to that volume is known to have nonunique solutions. Despite the nonuniqueness of the inversion we show that one may nevertheless uniquely determine certain moments of the vector spherical harmonic expansion of the current. It is demonstrated that the determination of these moments allows for the unique inversion of a current density confined to a spherical shell. Although unique the inversion may be ill conditioned and require a regularization of the inversion as demonstrated in an example numerical …

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Complex Multiplication Symmetry Of Black Hole Attractors, Monika Lynker, Vipul Periwal, Rolf Schimmrigk Sep 2003

Complex Multiplication Symmetry Of Black Hole Attractors, Monika Lynker, Vipul Periwal, Rolf Schimmrigk

Faculty Articles

We show how Moore’s observation, in the context of toroidal compactifications in type IIB string theory, concerning the complex multiplication structure of black hole attractor varieties, can be generalized to Calabi-Yau compactifications with finite fundamental groups. This generalization leads to an alternative general framework in terms of motives associated to a Calabi-Yau variety in which it is possible to address the arithmetic nature of the attractor varieties in a universal way via Deligne’s period conjecture.

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Optimization And Equilibrium Problems With Equilibrium Constraints, Boris S. Mordukhovich Sep 2003

Optimization And Equilibrium Problems With Equilibrium Constraints, Boris S. Mordukhovich

Mathematics Research Reports

The paper concerns optimization and equilibrium problems with the so-called equilibrium constraints (MPEC and EPEC), which frequently appear in applications to operations research. These classes of problems can be naturally unified in the framework of multiobjective optimization with constraints governed by parametric variational systems (generalized equations, variational inequalities, complementarity problems, etc.). We focus on necessary conditions for optimal solutions to MPECs and EPECs under general assumptions in finite-dimensional spaces. Since such problems are intrinsically nonsmooth, we use advanced tools of generalized differentiation to study optimal solutions by methods of modern variational analysis. The general results obtained are concretized for special …

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Essays On Minimum Cost Spanning Tree Games., Anirban Kar Dr. Aug 2003

Essays On Minimum Cost Spanning Tree Games., Anirban Kar Dr.

Doctoral Theses

There is a wide range of economic contexts in which aggregate costs have to be allocated amongst individual agents or components who derive t he benefits from a common project. A firm has to allocate overheard costs atmongst its different divisions. Regulatory authorities have to set taxes or fees on individual users for a variety of services. Partners in a joint venture must share costs (and benefits) of the joint venture. For example, when two doctors share an office they need to divide the cost of office space, medical equipment and secretarial help. If several municipalities use a common water …

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Sheep Updates 2003 - Wool, Richard Coole, Stephen Gherardi, Chris Oldham, K. Curtis, J. Stanton, Johan Greeff, Chris Oldham, Mike Hyder, Beth Pagamoni, Andrew Thompson, Tom Plaisted, Kazue Tanaka, Mike Ferguson, Darren Gordon, Andrew Peterson, Peter Sommerville Aug 2003

Sheep Updates 2003 - Wool, Richard Coole, Stephen Gherardi, Chris Oldham, K. Curtis, J. Stanton, Johan Greeff, Chris Oldham, Mike Hyder, Beth Pagamoni, Andrew Thompson, Tom Plaisted, Kazue Tanaka, Mike Ferguson, Darren Gordon, Andrew Peterson, Peter Sommerville

Sheep Updates

This session covers six papers from different authors:1.‘Pastures from space’ - an opportunity to increase the profitability of sheep production Richard Coole Farmer Kojonup W.A. Stephen Gherardi Chris Oldham Department of Agriculture Western Australia 2. K. Curtis Department of Agriculture WA J. Stanton Department of Agriculture WA and Curtin University 3. Is selection of ewe hogget replacement on measurement profitable? Johan Greeff Department of Agriculture of Western Australia 4. Optimising the nutrition/grazing management of ewe flocks Chris Oldham Mike Hyder Beth Paganoni Department of Agriculture of Western Australia Andrew Thompson Department of Primary Industries, Hamilton, Victoria Tom Plaisted Kazue Tanaka …

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Explaining And Predicting Patterns In Stochastic Population Systems, Shandelle M. Henson, Aaron A. King, R. F. Costantino, J. M. Cushing, Brian Dennis, Robert A. Desharnais Aug 2003

Explaining And Predicting Patterns In Stochastic Population Systems, Shandelle M. Henson, Aaron A. King, R. F. Costantino, J. M. Cushing, Brian Dennis, Robert A. Desharnais

Faculty Publications

Lattice effects in ecological time-series are patterns that arise because of the inherent discreteness of animal numbers. In this paper, we suggest a systematic approach for predicting lattice effects. We also show that an explanation of all the patterns in a population time-series may require more than one deterministic model, especially when the dynamics are complex.

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Fair-Weather Fans: The Correlation Between Attendance And Winning Percentage, Darren B. Glass Aug 2003

Fair-Weather Fans: The Correlation Between Attendance And Winning Percentage, Darren B. Glass

Math Faculty Publications

In Rob Neyer's chapter on San Francisco in his Big Book of Baseball Lineups, he speculates that there aren't really good baseball cities, and that attendance more closely correlates with winning percentage than with any other factor. He also suggests that a statistically minded person look at this. I took the challenge and have been playing with a lot of data.

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When Abelian Groups Split, Rachel M. Thomas, Robert C. Rhoades Aug 2003

When Abelian Groups Split, Rachel M. Thomas, Robert C. Rhoades

Mathematical Sciences Technical Reports (MSTR)

Let S be a hyperbolic surface tiled by kaleidoscopic triangles. Let Re denote the set of fixed points by the reflection in an edge, e, of a triangle. We say that Re is separating if S-Re has two components. Once we have a tiling, we can define a group of orientation preserving transformations, G. We develop a method for determining when a reflection is separating using the group algebra of G. Using this method we give necessary and sufficient conditions for a mirror to be separating when G is abelian. We also conjecture, that …

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Quantum Invariants Of Templates, Louis H. Kauffman, Masahico Saito, Michael C. Sullivan Aug 2003

Quantum Invariants Of Templates, Louis H. Kauffman, Masahico Saito, Michael C. Sullivan

Articles and Preprints

We define invariants for templates that appear in certain dynamical systems. Invariants are derived from certain bialgebras. Diagrammatic relations between projections of templates and the algebraic structures are used to define invariants. We also construct 3-manifolds via framed links associated to tamplate diagrams, so that any 3-manifold invariant can be used as a template invariant.

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Randomization Tests For Small Samples: An Application For Genetic Expression Data, Gary L. Gadbury, Grier P. Page, Moonseong Heo, John D. Mountz, David B. Allison Aug 2003

Randomization Tests For Small Samples: An Application For Genetic Expression Data, Gary L. Gadbury, Grier P. Page, Moonseong Heo, John D. Mountz, David B. Allison

Mathematics and Statistics Faculty Research & Creative Works

An advantage of randomization tests for small samples is that an exact P-value can be computed under an additive model. a disadvantage with very small sample sizes is that the resulting discrete distribution for P-values can make it mathematically impossible for a P-value to attain a particular degree of significance. We investigate a distribution of P-values that arises when several thousand randomization tests are conducted simultaneously using small samples, a situation that arises with microarray gene expression data. We show that the distribution yields valuable information regarding groups of genes that are differentially expressed between two groups: A treatment group …

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Modern Statistical Methods For Handling Missing Repeated Measurements In Obesity Trial Data: Beyond Locf, Gary L. Gadbury, C. S. Coffey, D. B. Allison Aug 2003

Modern Statistical Methods For Handling Missing Repeated Measurements In Obesity Trial Data: Beyond Locf, Gary L. Gadbury, C. S. Coffey, D. B. Allison

Mathematics and Statistics Faculty Research & Creative Works

This paper brings together some modern statistical methods to address the problem of missing data in obesity trials with repeated measurements. Such missing data occur when subjects miss one or more follow-up visits or drop out early from an obesity trial. a common approach to dealing with missing data because of dropout is 'last observation carried forward' (LOCF). This method, although intuitively appealing, requires restrictive assumptions to produce valid statistical conclusions. We review the need for obesity trials, the assumptions that must be made regarding missing data in such trials, and some modern statistical methods for analyzing data containing missing …

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A Probabilistic View Of Certain Weighted Fibonacci Sums, Arthur T. Benjamin, Judson D. Neer, Daniel T. Otero, James A. Sellers Aug 2003

A Probabilistic View Of Certain Weighted Fibonacci Sums, Arthur T. Benjamin, Judson D. Neer, Daniel T. Otero, James A. Sellers

All HMC Faculty Publications and Research

In this article, we pursue the reverse strategy of using probability to derive an and develop an exponential generating function for an in Section 3. In Section 4, we present a method for finding an exact, non-recursive, formula for an.

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Optimal Control Of Differential-Algebraic Inclusions, Boris S. Mordukhovich, Lianwen Wang Aug 2003

Optimal Control Of Differential-Algebraic Inclusions, Boris S. Mordukhovich, Lianwen Wang

Mathematics Research Reports

No abstract provided.

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Haplotyping And Minimum Diversity Graphs, C Davis, Allen G. Holder Jul 2003

Haplotyping And Minimum Diversity Graphs, C Davis, Allen G. Holder

Mathematics Faculty Research

Haplotyping is the process of reconstructing the genetic information donated by a prior generation to form a current population. Haplotyping is important because it allows us to study how traits are passed from one generation to another, which in turn allows us to find genetic markers that describe a current population's susceptibility to diseases. Our goal is to study the underlying graph theory problem, and we study the bipartite graphs, called diversity graphs, that describe haplotyping. In particular, we investigate the problem of finding the minimum number of haplotypes that can reconstruct a population, called the Pure Parsimony problem. The …

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The Kolmogorov Equation With Time-Measurable Coefficients, Jay Kovats Jul 2003

The Kolmogorov Equation With Time-Measurable Coefficients, Jay Kovats

Mathematics and System Engineering Faculty Publications

Using both probabilistic and classical analytic techniques, we investigate the parabolic Kolmogorov equation $$ L_t v +\frac {\partial v}{\partial t}\equiv \frac 12 a^{ij}(t)v_{x^ix^j} +b^i(t) v_{x^i} -c(t) v+ f(t) +\frac {\partial v}{\partial t}=0 $$ in $H_T:=(0,T) \times E_d$ and its solutions when the coefficients are bounded Borel measurable functions of $t$. We show that the probabilistic solution $v(t,x)$ defined in $\bar H_T$, is twice differentiable with respect to $x$, continuously in $(t,x)$, once differentiable with respect to $t$, a.e. $t \in [0,T)$ and satisfies the Kolmogorov equation $L_t v +\frac {\partial v}{\partial t}=0$ a.e. in $\bar H_T$. Our main tool will …

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Nonautonomous Difference Equations: Open Problems And Conjectures, Saber Elaydi Jul 2003

Nonautonomous Difference Equations: Open Problems And Conjectures, Saber Elaydi

Mathematics Faculty Research

Autonomous difference equations of the form xn+1 = ƒ (xn) may model populations of species with nonoverlaping generations such as fish, orchard pests, etc. The drawback of such models is that they do not account for environmental fluctuations or seasonal changes. Hence we are led to nonautonomous difference equations of the form xn+1 = ƒ (xn), n ∈ Ζ+. Our main focus in this note will be on periodic difference equations in which the sequence ƒn is periodic. Most of the open problems and conjectures in this …

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Is The World Evolving Discretely?, Saber Elaydi Jul 2003

Is The World Evolving Discretely?, Saber Elaydi

Mathematics Faculty Research

No abstract provided.

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On Adaptive Estimation In Orthogonal Saturated Designs, Weizhen Wang, Daniel T. Voss Jul 2003

On Adaptive Estimation In Orthogonal Saturated Designs, Weizhen Wang, Daniel T. Voss

Mathematics and Statistics Faculty Publications

A simple method is provided to construct a general class of individual and simultaneous confidence intervals for the effects in orthogonal saturated designs. These intervals use the data adaptively, maintain the confidence levels sharply at 1 - α at the least favorable parameter configuration, work effectively under effect sparsity, and include the intervals by Wang and Voss (2001) as a special case.

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Natural Superconvergent Points Of Triangular Finite Elements, Zhimin Zhang, Runchang Lin Jul 2003

Natural Superconvergent Points Of Triangular Finite Elements, Zhimin Zhang, Runchang Lin

Mathematics Research Reports

In this work, we analytically identify natural superconvergent points of function values and gradients for triangular elements. Both the Poisson equation and the Laplace equation are discussed for polynomial finite element spaces (with degrees up to 8) under four different mesh patterns. Our results verify computer findings of [2], especially, we confirm that the computed data have 9 digits of accuracy with an exception of one pair (which has 8-7 digits of accuracy). In addition, we demonstrate that the function value superconvergent points predicted by the symmetry theory [14] are the only superconvergent points for the Poisson equation. Finally, we …

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Using Reconstructability Analysis To Select Input Variables For Artificial Neural Networks, Stephen Shervais, Martin Zwick Jul 2003

Using Reconstructability Analysis To Select Input Variables For Artificial Neural Networks, Stephen Shervais, Martin Zwick

Complex Systems Faculty Publications and Presentations

We demonstrate the use of Reconstructability Analysis to reduce the number of input variables for a neural network. Using the heart disease dataset we reduce the number of independent variables from 13 to two, while providing results that are statistically indistinguishable from those of NNs using the full variable set. We also demonstrate that rule lookup tables obtained directly from the data for the RA models are almost as effective as NNs trained on model variables.

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On The Stability Of The Positive Radial Steady States For A Semilinear Cauchy Problem, Yinbin Deng, Yi Li, Yi Liu Jul 2003

On The Stability Of The Positive Radial Steady States For A Semilinear Cauchy Problem, Yinbin Deng, Yi Li, Yi Liu

Mathematics and Statistics Faculty Publications

No abstract provided.

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A Forward-Backward Fluence Model For The Low-Energy Neutron Boltzmann Equation, Gary Alan Feldman Jul 2003

A Forward-Backward Fluence Model For The Low-Energy Neutron Boltzmann Equation, Gary Alan Feldman

Mathematics & Statistics Theses & Dissertations

In this research work, the neutron Boltzmann equation was separated into two coupled integro-differential equations describing forward and backward neutron fluence in selected materials. Linear B-splines were used to change the integro-differential equations into a coupled system of ordinary differential equations (O.D.E.'s). Difference approximations were then used to recast the O.D.E.'s into a coupled system of linear equations that were solved for forward and backward neutron fluences. Adding forward and backward fluences gave the total fluence at selected energies and depths in the material. Neutron fluences were computed in single material shields and in a shield followed by a target …

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Superconvergence Of Iterated Solutions For Linear And Nonlinear Integral Equations: Wavelet Applications, Boriboon Novaprateep Jul 2003

Superconvergence Of Iterated Solutions For Linear And Nonlinear Integral Equations: Wavelet Applications, Boriboon Novaprateep

Mathematics & Statistics Theses & Dissertations

In this dissertation, we develop the Petrov-Galerkin method and the iterated Petrov-Galerkin method for a class of nonlinear Hammerstein equation. We also investigate the superconvergence phenomenon of the iterated Petrov-Galerkin and degenerate kernel numerical solutions of linear and nonlinear integral equations with a class of wavelet basis. The Fredholm integral equations and the Hammerstein equations are considered in linear and nonlinear cases respectively. Alpert demonstrated that an application of a class of wavelet basis elements in the Galerkin approximation of the Fredholm equation of the second kind leads to a system of linear equations which is sparse. The main concern …

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Some Issues On Time Varying Risk Premium In Arch-M Model., Samarjit Das Dr. Jun 2003

Some Issues On Time Varying Risk Premium In Arch-M Model., Samarjit Das Dr.

Doctoral Theses

Since the 1970's it has been observed in many economies that financial and macroeconomic variables like equity prices, treasury bill rates and exchange rates have become more and more volatile in nature. This may be due tumor flexible monetary policies pursued in these countries as well as due to their increasing exposure towards various international developments. Accordingly, economic agents are facing increasingly more and more risky environment. Re- searchers as well as professional economists in the area of capital and business finance have, therefore, been increasingly attracted in recent years towards studying the effect of risk and uncertainty on asset …

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Open Problems From Cccg 2002, Erik D. Demaine, Joseph O'Rourke Jun 2003

Open Problems From Cccg 2002, Erik D. Demaine, Joseph O'Rourke

Computer Science: Faculty Publications

No abstract provided.

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The Topology Of Hyperbolic Attractors On Compact Surfaces, Todd L. Fisher Jun 2003

The Topology Of Hyperbolic Attractors On Compact Surfaces, Todd L. Fisher

Faculty Publications

Suppose M is a compact surface and M is a nontrivial mixing hyperbolic attractor for some f 2 Diff(M). We show that if is a hyperbolic set for some g 2 Diff(M), then is a nontrivial mixing hyperbolic attractor or repeller for g.

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Minimal Graphs In R3 Over Convex Domains, Michael Dorff Jun 2003

Minimal Graphs In R3 Over Convex Domains, Michael Dorff

Faculty Publications

Krust established that all conjugate and associate surfaces of a minimal graph over a convex domain are also graphs. Using a convolution theorem from the theory of harmonic univalent mappings, we generalize Krust's theorem to include the family of convolution surfaces which are generated by taking the Hadamard product or convolution of mappings. Since this convolution involves convex univalent analytic mappings, this family of convolution surfaces is much larger than just the family of associated surfaces. Also, this generalization guarantees that all the resulting surfaces are over close-toconvex domains. In particular, all the associate surfaces and certain Goursat transformation surfaces …

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Orthogonal Macroelement Scaling Vectors And Wavelets In 1-D, Douglas P. Hardin, Bruce Kessler Jun 2003

Orthogonal Macroelement Scaling Vectors And Wavelets In 1-D, Douglas P. Hardin, Bruce Kessler

Mathematics Faculty Publications

We develop a {\em macroelement} based technique for constructing orthogonal univariate multiwavelets. We illustrate the technique with two examples. In the first example we provide a new construction of the symmetric, orthogonal, continuous scaling vector given in \cite{GHM}. In the second example, we construct a continuous orthogonal scaling vector with three components. The components of this scaling vector are symmetric or antisymmetric and provide approximation order 3, (equivalently, the components of $\Psi$ are orthogonal to polynomials of degree 2 or less.) We believe this second example to be new.

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The Fibonacci Numbers -- Exposed More Discretely, Arthur T. Benjamin, Jennifer J. Quinn Jun 2003

The Fibonacci Numbers -- Exposed More Discretely, Arthur T. Benjamin, Jennifer J. Quinn

All HMC Faculty Publications and Research

No abstract provided in this article.

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Validation Of The A Posteriori Error Estimator Based On Polynomial Preserving Recovery For Linear Elements, Zhimin Zhang, Ahmed Naga Jun 2003

Validation Of The A Posteriori Error Estimator Based On Polynomial Preserving Recovery For Linear Elements, Zhimin Zhang, Ahmed Naga

Mathematics Research Reports

In this paper the quality of the error estimator based on the Polynomial Preserving Recovery (PPR) is investigated using the computer-based approach proposed by Babiiska et al. A comparison is made between the error estimator based on the PPR and the one based on the Superconvergence Patch Recovery (SPR). It was found that the PPR is at least as good as the SPR.

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