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Mathematics & Statistics

Modeling & simulation research

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Displaying 451 - 475 of 489

Measuring the Utility/Path Diversity Tradeoff in Multipath Protocols

October 20, 2009
Author(s)
Fern Y. Hunt, Vladimir V. Marbukh
We derive a model of congestion control where the trade-off between utility and path diversity can be investigated. In a network where there can be multiple routes between locations, each source is assigned a route according to a random allocation scheme

Fast Iterative Solver for Convection-Diffusion Systems with Spectral Elements

October 16, 2009
Author(s)
Aaron Lott, Howard Elman
We introduce a solver and preconditioning technique based on Domain Decomposition and the Fast Diagonalization Method that can be applied to tensor product based discretizations of the steady convection-diffusion equation. The method is based on iterative

Spectrum Simulation in DTSA-II

October 1, 2009
Author(s)
Nicholas W. Ritchie
Spectrum simulation is a useful practical and pedagogical tool. Particularly with complex samples or trace constituents, a simulation can help to understand the limits of the technique and how to optimize the tools for the optimal measurement. DTSA-II

Gauging the Repeatability of 3D Imaging Systems by Sphere Fitting

September 30, 2009
Author(s)
Marek Franaszek, Geraldine S. Cheok, Kamel S. Saidi
Multiple scans of the same object acquired with 3D imaging system (e.g., laser scanner) in the same experimental conditions could provide valuable information about the instrument s performance (e.g., stability, existence of bias, measurement error)

A Combinatorial Approach to Building Navigation Graphs for Dynamic Web Applications

September 20, 2009
Author(s)
Raghu N. Kacker, David R. Kuhn, James F. Lawrence, Wenhua Wang, Yu Lei, Sreedevi Sampath
Modeling the navigation structure of a dynamic web application is a challenging task because of the presence of dynamic pages. In particular, there are two problems to be dealt with: (1) the page explosion problem, i.e., the number of dynamic pages may be

Estimating Volumes of Simulated Lung Cancer Nodules

July 15, 2009
Author(s)
David E. Gilsinn, Bruce R. Borchardt, Amelia Tebbe
Lung cancer is a disease of uncontrolled cell growth in tissues of the lung. Computed tomography (CT) shows promise in detecting lung cancers at earlier, more operable stages, when survival is better. CT scans generate multiple 2-D slice images of the lung

Design of the DEMO Fusion Reactor Following ITER

July 1, 2009
Author(s)
Geoffrey B. McFadden, Paul R. Garabedian
Runs of the NSTAB equilibrium and stability code show there are many 3D solutions of the advanced tokamak problem subject to axially symmetric boundary conditions. These numerical simulations based on mathematical equations in conservation form predict

Sensitivities and Variances for Fitted Parameters of Spheres

July 1, 2009
Author(s)
Christoph J. Witzgall, Marek Franaszek
Experimental data have been gathered by applying 3D imaging systems, such as LIDAR/LADAR instruments, to spherical objects. This report provides a compilation of the statistical and analytical procedures to be used for an evaluation, to be reported

Laboratory Effects Models for Interlaboratory Comparisons

June 16, 2009
Author(s)
Blaza Toman, Antonio M. Possolo
Statistical analysis of inter-laboratory comparisons (e.g. Key Comparisons, Supplemental Comparisons) is required to produce an estimate of the measurand called a reference value and further, measures of equivalence of the participating laboratories

Atmospheric Retention of Man-made CO 2 Emissions

June 8, 2009
Author(s)
Bert W. Rust
Rust and Thijsse have shown that global annual average temperature anomalies T(t i) vary linearly with atmospheric CO 2 concentrations c(t i). The c(t i) can be related to man-made CO 2 emissions F(t i) by a linear regression model whose solution vector

Markov Chain Analysis for Large-Scale Grid Systems

April 20, 2009
Author(s)
Christopher E. Dabrowski, Fern Y. Hunt
In large-scale grid systems with decentralized control, the interactions of many service providers and consumers will likely lead to emergent global system behaviours that result in unpredictable, often detrimental outcomes. This possibility argues for

Modeling of Photochemical Reactions in a Focused Laser Beam

July 1, 2007
Author(s)
Fern Y. Hunt, Adolfas Gaigalas, Lili Wang
This paper presents a mathematical model of photodegradation of fluorophores passing through a laser beam. The beam is focused on the sample and thus the power distribution of incident light is strongly dependent on spatial location while the fluorophores

Multiscale Model of Germanium Quantum Dots in Silicon

March 1, 2007
Author(s)
David T. Read, Vinod Tewary
Atomic displacements, strains and strain energies in the neighborhood of near-spherical, coherent germanium ¿quantum dots¿ (QD) in crystalline silicon and near a 001} Si surface have been predicted by multiscale modeling, using a combination of classical

Cell Morphology and Migration Linked to Substrate Rigidity

January 1, 2007
Author(s)
Yong Ni, Martin Chiang
A mathematical model, based on thermodynamics, was developed to demonstrate the substrate mechanics influences the cell morphology and migration. The mechanisms by which substrate rigidity are translated into cell morphological changes and cell movement

Approximating Periodic Solutions of Autonomous Delay Differential Equations

November 30, 2006
Author(s)
David E. Gilsinn
Machine tool chatter has been characterized as isolated periodic solutions or limit cycles of delay differential equations. Determining the amplitude and frequency of the limit cycle is sometimes crucial to understanding and controlling the stability of

Integral Operators and Delay Differential Equations

October 1, 2006
Author(s)
David E. Gilsinn, Florian A. Potra
We begin this expository essay by reviewing with examples what a typical engineer already knows about statistics. We then consider a central question in engineering decision making, i.e., given a computer simulation of high-consequence systems, how do we

Pose of I-Beams for Construction Site Automation

September 21, 2004
Author(s)
David E. Gilsinn, Geraldine S. Cheok, Alan M. Lytle
Automation of construction processes can result in reduced project costs and increased worker safety. A process that lends itself to automation is the picking and placing of objects. However, determining the pose (position and orientation) of an object is
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