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Articles 6211 - 6240 of 7997

Full-Text Articles in Physical Sciences and Mathematics

The Weak Euler Scheme For Stochastic Delay Equations, Evelyn Buckwar, Rachel Kuske, Salah-Eldin A. Mohammed, Tony Shardlow May 2008

The Weak Euler Scheme For Stochastic Delay Equations, Evelyn Buckwar, Rachel Kuske, Salah-Eldin A. Mohammed, Tony Shardlow

Articles and Preprints

We study weak convergence of an Euler scheme for non-linear stochastic delay differential equations (SDDEs) driven by multidimensional Brownian motion. The Euler scheme has weak order of convergence 1, as in the case of stochastic ordinary differential equations (SODEs) (i.e., without delay). The result holds for SDDEs with multiple finite fixed delays in the drift and diffusion terms. Although the set-up is non-anticipating, our approach uses the Malliavin calculus and the anticipating stochastic analysis techniques of Nualart and Pardoux.

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A Monte Carlo Power Analysis Of Traditional Repeated Measures And Hierarchical Multivariate Linear Models In Longitudinal Data Analysis, Hua Fang, Gordon P. Brooks, Maria L. Rizzo, Kimberly A. Espy, Robert S. Barcikowski May 2008

A Monte Carlo Power Analysis Of Traditional Repeated Measures And Hierarchical Multivariate Linear Models In Longitudinal Data Analysis, Hua Fang, Gordon P. Brooks, Maria L. Rizzo, Kimberly A. Espy, Robert S. Barcikowski

Developmental Cognitive Neuroscience Laboratory: Faculty and Staff Publications

The power properties of traditional repeated measures and hierarchical linear models have not been clearly determined in the balanced design for longitudinal studies in the current literature. A Monte Carlo power analysis of traditional repeated measures and hierarchical multivariate linear models are presented under three variance-covariance structures. Results suggest that traditional repeated measures have higher power than hierarchical linear models for main effects, but lower power for interaction effects. Significant power differences are also exhibited when power is compared across different covariance structures. Results also supplement more comprehensive empirical indexes for estimating model precision via bootstrap estimates and the approximate …

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The Signed-Graphic Representations Of Wheels And Whirls, Dan Slilaty, Hongxun Qin May 2008

The Signed-Graphic Representations Of Wheels And Whirls, Dan Slilaty, Hongxun Qin

Mathematics and Statistics Faculty Publications

We characterize all of the ways to represent the wheel matroids and whirl matroids using frame matroids of signed graphs. The characterization of wheels is in terms of topological duality in the projective plane and the characterization of whirls is in terms of topological duality in the annulus.

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Connectivity In Frame Matroids, Dan Slilaty, Hongxun Qin May 2008

Connectivity In Frame Matroids, Dan Slilaty, Hongxun Qin

Mathematics and Statistics Faculty Publications

We discuss the relationship between the vertical connectivity of a biased graph Ω and the Tutte connectivity of the frame matroid of Ω (also known as the bias matroid of Ω).

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Ordered Matrices Of Prescribed Row And Column Sum, Janine Janoski May 2008

Ordered Matrices Of Prescribed Row And Column Sum, Janine Janoski

All Theses

Let M(n,s) be the number of nxn matrices with binary entries, row and column sum s, and whose rows are in lexicographical order. Let S(n) be the number of nxn matrices with entries from {0,1,2}, symmetric, with trace 0, and row sum 2. (The sequence S(n) appears as A002137 in N.J.A. Sloane's Online Encyclopedia of Integer Sequences.)
We give two proofs to show that M(n,2)=S(n). First, we show they satisfy the same recurrence. Second, we give an explicit bijection between the two sets. We also show that the bijection maintains the cycle structure of our matrices.
Let M_s(n,2) be the …

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Dow Jones Index, Garch(1,1) And Change-Points, Tharanga Wickramarachchi May 2008

Dow Jones Index, Garch(1,1) And Change-Points, Tharanga Wickramarachchi

All Theses

Many econometric time series data sets, such as log returns of stocks, exhibit evidence of the so called stylized facts. Namely it is generally observed that the data itself is uncorrelated with heavy tails, but the squared data has signicant autocorrelation. For such data sets, there appears to be little or no linear information in the past about the future values of the series. Thus the class of Autoregressive Integrated moving average models (ARIMA) are not appropriate. However, there does in general appear to be information in past values of the squared data about future values of the squared data. …

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Methods Of Assessing And Ranking Probable Sources Of Error, Nataniel Greene May 2008

Methods Of Assessing And Ranking Probable Sources Of Error, Nataniel Greene

Publications and Research

A classical method for ranking n potential events as sources of error is Bayes' theorem. However, a ranking based on Bayes' theorem lacks a fundamental symmetry: the ranking in terms of blame for error will not be the reverse of the ranking in terms of credit for lack of error. While this is not a flaw in Bayes' theorem, it does lead one to inquire whether there are related methods which have such symmetry. Related methods explored here include the logical version of Bayes' theorem based on probabilities of conditionals, probabilities of biconditionals, and ratios or differences of credit to …

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Studies Of Laser Wakefield Structures And Electron Acceleration In Underdense Plasmas, Anatoly Maksimchuk, Steven A. Reed, Stepan S. Bulanov, Vladimir Chvykov, Galina Kalintchenko, Takeshi Matsuoka, Christopher Mcguffey, Gerard Mourou, Natalia Naumova, John Nees, Pascal Rousseau, Victor Yanovsky, Karl Krushelnick, Nicholas H. Matlis, Serguei Y. Kalmykov, Gennady Shvets, Michael C. Downer, C. R. Vane, J. R. Beene, Daniel W. Stracener, David R. Schultz Apr 2008

Studies Of Laser Wakefield Structures And Electron Acceleration In Underdense Plasmas, Anatoly Maksimchuk, Steven A. Reed, Stepan S. Bulanov, Vladimir Chvykov, Galina Kalintchenko, Takeshi Matsuoka, Christopher Mcguffey, Gerard Mourou, Natalia Naumova, John Nees, Pascal Rousseau, Victor Yanovsky, Karl Krushelnick, Nicholas H. Matlis, Serguei Y. Kalmykov, Gennady Shvets, Michael C. Downer, C. R. Vane, J. R. Beene, Daniel W. Stracener, David R. Schultz

Serge Youri Kalmykov

Experiments on electron acceleration and optical diagnostics of laser wakes were performed on the HERCULES facility in a wide range of laser and plasma parameters. Using frequency domain holography we demonstrated single shot visualization of individual plasma waves, produced by 40 TW, 30 fs laser pulses focused to the intensity of 10^{19} W/cm^2 onto a supersonic He gas jet with plasma densities n_e ~ 10^{19} cm^{−3}. These holographic “snapshots” capture the variation in shape of the plasma wave with distance behind the driver, and resolve wave front curvature seen previously only in simulations. High-energy quasimonoenergetic electron beams were generated using …

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Caching And Distributing Statistical Analyses In R, Roger D. Peng Apr 2008

Caching And Distributing Statistical Analyses In R, Roger D. Peng

Johns Hopkins University, Dept. of Biostatistics Working Papers

We present the cacher package for \proglang{R}, which provides tools for caching statistical analyses and for distributing these analyses to others in an efficient manner. The cacher package takes objects created by evaluating R expressions and stores them in key-value databases. These databases of cached objects can subsequently be assembled into packages for distribution over the web. The cacher package also provides tools to help readers examine the data and code in a statistical analysis and reproduce, modify, or improve upon the results. In addition, readers can easily conduct alternate analyses of the data. We describe the design and implementation …

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Traveling Waves And Shocks In A Viscoelastic Generalization Of Burgers' Equation, Victor Camacho '07, Robert D. Guy, Jon T. Jacobsen Apr 2008

Traveling Waves And Shocks In A Viscoelastic Generalization Of Burgers' Equation, Victor Camacho '07, Robert D. Guy, Jon T. Jacobsen

All HMC Faculty Publications and Research

We consider traveling wave phenomena for a viscoelastic generalization of Burgers' equation. For asymptotically constant velocity profiles we find three classes of solutions corresponding to smooth traveling waves, piecewise smooth waves, and piecewise constant (shock) solutions. Each solution type is possible for a given pair of asymptotic limits, and we characterize the dynamics in terms of the relaxation time and viscosity.

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Yupanchis: La Matemática Inca Y Su Incorporación A La Clase, Yonit Bousany Apr 2008

Yupanchis: La Matemática Inca Y Su Incorporación A La Clase, Yonit Bousany

Independent Study Project (ISP) Collection

Este diálogo tuve con una estudiante de quinto grado de la escuela intercultural-bilingüe Wiñaypaq, a quien veía cada día luchando con la matemática. Sus respuestas señalan bastante sobre su experiencia escolar, especialmente porque, desafortunadamente, la mayoría de experiencias de niños quechua-hablantes en clases de matemática son indeseables en el Perú. Por una variedad de razones, niños peruanos quechua-hablantes raras veces suceden en alcanzar un nivel avanzado en el aprendizaje de las Matemáticas. Podemos atribuir este hecho a variables sociológicos, políticos, lingüísticos y/o económicos, pero no, como es una opinión popular, a una falta de una fuerte base de conceptos matemáticos …

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A Wavelet-Based Method For Overcoming The Gibbs Phenomenon, Nataniel Greene Mar 2008

A Wavelet-Based Method For Overcoming The Gibbs Phenomenon, Nataniel Greene

Publications and Research

The Gibbs phenomenon refers to the lack of uniform convergence which occurs in many orthogonal basis approximations to piecewise smooth functions. This lack of uniform convergence manifests itself in spurious oscillations near the points of discontinuity and a low order of convergence away from the discontinuities. Here we describe a numerical procedure for overcoming the Gibbs phenomenon called the inverse wavelet reconstruction method. The method takes the Fourier coefficients of an oscillatory partial sum and uses them to construct the wavelet coefficients of a non-oscillatory wavelet series.

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Estimation Of The Number Of Microbial Species Comprising A Population, Melanie R. Slattery Mar 2008

Estimation Of The Number Of Microbial Species Comprising A Population, Melanie R. Slattery

Theses and Dissertations

The purpose of this research was to evaluate the appropriateness of using non-parametric estimators, specifically the Chao1, ACES, and Jackknife methods, for estimation of the number of unique species comprising a population. It goes on to develop a parametric method for the above stated problem. This research consisted of creating diverse populations, with known numbers of species, and applying the aforementioned non-parametric and parametric methods to samples drawn from the constructed populations. The parametric fitting of several different distributions to the sample data, including the lognormal, gamma, and Weibull was considered. Both types of methodologies were then applied to sample …

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Delay-Induced Instabilities In Self-Propelling Swarms, Eric Forgoston, Ira B. Schwartz Mar 2008

Delay-Induced Instabilities In Self-Propelling Swarms, Eric Forgoston, Ira B. Schwartz

Department of Applied Mathematics and Statistics Faculty Scholarship and Creative Works

We consider a general model of self-propelling particles interacting through a pairwise attractive force in the presence of noise and communication time delay. Previous work by Erdmann [Phys. Rev. E 71, 051904 (2005)] has shown that a large enough noise intensity will cause a translating swarm of individuals to transition to a rotating swarm with a stationary center of mass. We show that with the addition of a time delay, the model possesses a transition that depends on the size of the coupling amplitude. This transition is independent of the initial swarm state (traveling or rotating) and is characterized by …

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Proceedings From Scientific Conference On Green Energy And It, Dr. Erik Dahlquist Mar 2008

Proceedings From Scientific Conference On Green Energy And It, Dr. Erik Dahlquist

Dr. Erik Dahlquist

This conference is part of the annual Energitinget, a national arena for energy in Sweden, with some 2500 participants. The focus with this session is to give a forum for researchers to present scientific results, and also to discuss these with other researchers. It contains papers in the area of Energy and IT as well as Green energy generally

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Failure Of Metric Regularity For Major Classes Of Variational Systems, Boris S. Mordukhovich Mar 2008

Failure Of Metric Regularity For Major Classes Of Variational Systems, Boris S. Mordukhovich

Mathematics Research Reports

The paper is devoted to the study of metric regularity, which is a remarkable property of set-valued mappings playing an important role in many aspects of nonlinear analysis and its applications. We pay the main attention to metric regularity of the so- called parametric variational systems that contain, in particular, various classes of parameterized/perturbed variational and hemivariational inequalities, complementarity systems, sets of optimal solutions and corresponding Lagrange multipliers in problems of parametric optimization and equilibria, etc. Based on the advanced machinery of generalized differentiation1 we surprisingly reveal that metric regularity fails for certain major classes of parametric variational systems, which …

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First Solutions To Gravitation And Orbital Precession Under Vectorial Relativity, Jorge A. Franco Mar 2008

First Solutions To Gravitation And Orbital Precession Under Vectorial Relativity, Jorge A. Franco

Jorge A Franco

One of the reasons of the success of Einstein’s General Theory of Relativity (GTR) was that it allowed to calculate planet’s precession (rotation of the elliptical path axis with time, i.e.: Mercury Precession). The fact that its occurrence has been experimentally observed is not accounted by classic Kepler’s or Newton Laws because it is only applicable to constant masses. This work shows that planet’s precession is a direct consequence of considering variable planet’s mass inside accepted physical laws in our known three-dimensional space. According to us, this work positively confirms new definitions of mass and Energy obtained under Vectorial Relativity.

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An Overview Of Conditionals And Biconditionals In Probability, Nataniel Greene Mar 2008

An Overview Of Conditionals And Biconditionals In Probability, Nataniel Greene

Publications and Research

Conditional and biconditional statements are a standard part of symbolic logic but they have only recently begun to be explored in probability for applications in artificial intelligence. Here we give a brief overview of the major theorems involved and illustrate them using two standard model problems from conditional probability.

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Street Gangs: A Modeling Approach To Evaluation "At Risk" Youth, Bernard Jacob Loeffelholz Mar 2008

Street Gangs: A Modeling Approach To Evaluation "At Risk" Youth, Bernard Jacob Loeffelholz

Theses and Dissertations

Street gangs have plagued the United States for decades. One focus of current gang prevention efforts strives to reduce the number of new recruits to local street gangs. This research proposes the uses of modeling and decision analysis to aid in identifying potentially “at risk” children likely to join a street gang in Montgomery County, Ohio. A stronger means of identification of “at risk” children can lead to a more efficient placement of resources to reduce the number of street gang recruits. The approach also aids in differentiating between neighborhoods to help focus efforts. Information obtained from value-focused thinking (VFT) …

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Statistical Removal Of Shadow For Applications To Gait Recognition, Brian D. Hockersmith Mar 2008

Statistical Removal Of Shadow For Applications To Gait Recognition, Brian D. Hockersmith

Theses and Dissertations

The purpose of this thesis is to mathematically remove the shadow of an individual on video. The removal of the shadow will aid in the rendering of higher quality binary silhouettes than previously allowed. These silhouettes will allow researchers studying gait recognition to work with silhouettes unhindered by unrelated data. The thesis begins with the analysis of videos of solid colored backgrounds. A formulation of the effect of shadow on specified colors will aid in the derivation of a hypothesis test to remove an individual’s shadow. Video of an individual walking normally, perpendicular to the camera will be utilized to …

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Entire Blow-Up Solutions Of Semilinear Elliptic Equations And Systems, Jesse D. Peterson Mar 2008

Entire Blow-Up Solutions Of Semilinear Elliptic Equations And Systems, Jesse D. Peterson

Theses and Dissertations

We examine two problems concerning semilinear elliptic equations. We consider single equations of the form Δu = p(x)uα + q(x)uβ for 0 <α ≤ β ≤1 and systems Δu = p(| x |) f (v), Δv = q(| x |)g(u) , both in Euclidean n -space, n ≥ 3 . These types of problems arise in steady state diffusion, the electric potential of some bodies, subsonic motion of gases, and control theory. For the single equation case, we present sufficient conditions on p and q to …

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Risk-Based Comparison Of Classification Systems, Seth B. Wagenman Mar 2008

Risk-Based Comparison Of Classification Systems, Seth B. Wagenman

Theses and Dissertations

Performance measures for families of classification system families that rely upon the analysis of receiver operating characteristics (ROCs), such as area under the ROC curve (AUC), often fail to fully address the issue of risk, especially for classification systems involving more than two classes. For the general case, we denote matrices of class prevalences, costs, and class-conditional probabilities, and assume costs are subjectively fixed, acceptable estimates for expected values of class-conditional probabilities exist, and mutual independence between a variable in one such matrix and those of any other matrix. The ROC Risk Functional (RRF), valid for any finite number of …

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Hardware Algorithm Implementation For Mission Specific Processing, Jason W. Shirley Mar 2008

Hardware Algorithm Implementation For Mission Specific Processing, Jason W. Shirley

Theses and Dissertations

There is a need to expedite the process of designing military hardware to stay ahead of the adversary. The core of this project was to build reusable, synthesizeable libraries to make this a possibility. In order to build these libraries, Matlab® commands and functions, such as Conv2, Round, Floor, Pinv, etc., had to be converted into reusable VHDL modules. These modules make up reusable libraries for the Mission Specific Process (MSP) which will support AFRL/RY. The MSP allows the VLSI design process to be completed in a mere matter of days or months using an FPGA or ASIC design, as …

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A Method For Visualizing Multivariate Time Series Data, Roger D. Peng Feb 2008

A Method For Visualizing Multivariate Time Series Data, Roger D. Peng

Johns Hopkins University, Dept. of Biostatistics Working Papers

Visualization and exploratory analysis is an important part of any data analysis and is made more challenging when the data are voluminous and high-dimensional. One such example is environmental monitoring data, which are often collected over time and at multiple locations, resulting in a geographically indexed multivariate time series. Financial data, although not necessarily containing a geographic component, present another source of high-volume multivariate time series data. We present the mvtsplot function which provides a method for visualizing multivariate time series data. We outline the basic design concepts and provide some examples of its usage by applying it to a …

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Microproteomics: Analysis Of Protein Diversity In Small Samples, Howard B. Gutstein, Jeffrey S. Morris, Suresh P. Annangudi, Jonathan V. Sweedler Feb 2008

Microproteomics: Analysis Of Protein Diversity In Small Samples, Howard B. Gutstein, Jeffrey S. Morris, Suresh P. Annangudi, Jonathan V. Sweedler

Jeffrey S. Morris

Proteomics, the large-scale study of protein expression in organisms, offers the potential to evaluate global changes in protein expression and their post-translational modifications that take place in response to normal or pathological stimuli. One challenge has been the requirement for substantial amounts of tissue in order to perform comprehensive proteomic characterization. In heterogeneous tissues, such as brain, this has limited the application of proteomic methodologies. Efforts to adapt standard methods of tissue sampling, protein extraction, arraying, and identification are reviewed, with an emphasis on those appropriate to smaller samples ranging in size from several microliters down to single cells. The …

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Local Cohomology And Support For Triangulated Categories, Dave Benson, Srikanth Iyengar, Henning Krause Feb 2008

Local Cohomology And Support For Triangulated Categories, Dave Benson, Srikanth Iyengar, Henning Krause

Department of Mathematics: Faculty Publications

We propose a new method for defining a notion of support for objects in any compactly generated triangulated category admitting small coproducts. This approach is based on a construction of local cohomology functors on triangulated categories, with respect to a central ring of operators. Suitably specialized one recovers, for example, the theory for commutative noetherian rings due to Foxby and Neeman, the theory of Avramov and Buchweitz for complete intersection local rings, and varieties for representations of finite groups according to Benson, Carlson, and Rickard. We give explicit examples of objects whose triangulated support and cohomological support differ. In the …

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Comment On Global Dynamics Of Biological Systems, Radhakrishnan Nagarajan Feb 2008

Comment On Global Dynamics Of Biological Systems, Radhakrishnan Nagarajan

Radhakrishnan Nagarajan

No abstract provided.

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Grain Growth And Texture Development In Lithium Fluoride Thin Films, Hakkwan Kim, Alexander H. King Feb 2008

Grain Growth And Texture Development In Lithium Fluoride Thin Films, Hakkwan Kim, Alexander H. King

Alexander H. King

We have studied grain-growth and texture development in polycrystalline lithium fluoride thin films using dark-field transmission electron microscopy. We demonstrate that we can isolate the size distribution of 〈111〉 surface normal grains from the overall size distribution, based on simple and plausible assumptions about the texture. The {111} texture formation and surface morphology were also observed by x-ray diffraction and atomic force microscopy, respectively. The grain-size distributions become clearly bimodal as the annealing time increases, and we deduce that the short-time size distributions are also a sum of two overlapping peaks. The smaller grain-size peak in the distribution corresponds to …

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Fourier Series Of Orthogonal Polynomials, Nataniel Greene Feb 2008

Fourier Series Of Orthogonal Polynomials, Nataniel Greene

Publications and Research

Explicit formulas for the Fourier coefficients of the Legendre polynomials can be found in the Bateman Manuscript Project. However, similar formulas for more general classes of orthogonal polynomials do not appear to have been worked out. Here we derive explicit formulas for the Fourier series of Gegenbauer, Jacobi, Laguerre and Hermite polynomials.

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Computing Equilibria Of N-Player Games With Arbitrary Accuracy,, Srihari Govindan, Robert B. Wilson Jan 2008

Computing Equilibria Of N-Player Games With Arbitrary Accuracy,, Srihari Govindan, Robert B. Wilson

Robert B Wilson

From a variant of Kuhn's triangulation we derive a discrete version of the Global Newton Method that yields an epsilon-equilibrium of an N-player game and then sequentially reduces epsilon toward zero to obtain any desired precision or the best precision for any number of iterations.

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