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Mathematics & Statistics

Modeling & simulation research

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Displaying 201 - 225 of 493

Model-based Cosimulation for Industrial Wireless Networks

June 15, 2018
Author(s)
Ging Jeng, Honglei Li, Yanzhou Liu, Yongkang Liu, Mohamed Hany, Rick Candell, Shuvra Bhattacharyya
Wireless communications technology has the potential to provide major benefits in lowering the cost and increasing the efficiency of factory automation (FA) systems. However, design of FA systems that employ wireless networks involves stringent constraints

Energy Renormalization Method for the Coarse-Graining of Polymer Viscoelasticity

May 10, 2018
Author(s)
Jake Song, David D. Hsu, Kenneth R. Shull, Frederick R. Phelan Jr., Jack F. Douglas, Wenjie Xia, Sinan Keten
Developing time and temperature transferable coarse-grained (CG) models is essential for the computational prediction and design of polymeric glass-forming materials, but this goal has remained elusive. The dynamics of CG models are often greatly altered

Evaluating Predictors of Congestion Collapse in Communication Networks

April 23, 2018
Author(s)
Christopher E. Dabrowski, Kevin L. Mills
Researchers model congestion in communication networks using a percolation process, where congestion spreads minimally before a critical load and expands rapidly afterwards. Some studies identify precursor signals arising near critical load, but none

Refined Calculations of Synchrotron Radiation for NISTs SURF III Facility

April 16, 2018
Author(s)
Eric L. Shirley, Mitchell L. Furst, Uwe Arp
We have developed a new method for exact calculation of synchrotron radiation for the National Institute of Standards and Technology Synchrotron Ultraviolet Radiation Facility, SURF III. Instead of using the Schwinger formula, which is only an

UNCERTAINTY IN MULTI-SCALE CREEP RUPTURE LIFE MODELING AND A NEW APPROACH TO ESTIMATING FREQUENCY OF IN-SERVICE INSPECTION OF COMPONENTS AT ELEVATED TEMPERATURES (*)

April 3, 2018
Author(s)
Jeffrey T. Fong, Nathanael A. Heckert, James J. Filliben, Marvin J. Cohn
Uncertainty in modeling the creep rupture life of a full-scale component using experimental data at microscopic (Level 1), specimen (Level 2), and full-size (Level 3) scales, is addressed by applying statistical theory of prediction intervals, and that of

Metastable morphological states of catalytic nanoparticles

March 1, 2018
Author(s)
Pin A. Lin, Bharath N. Natarajan, Michael P. Zwolak, Renu Sharma
During the catalytic synthesis of graphene, nanotubes, fibers, and other nanostructures, many intriguing phenomena occur, such as phase separation, precipitation, and processes similar to capillary action. The underlying mechanism of these processes and

Semiempirical Configuration Interaction Calculations for RuCentered Dyes

February 18, 2018
Author(s)
Lisa A. Fredin, Thomas C. Allison
Computational investigation of of the photochemical properties of transition-metal-centered dyes typically involves optimization of the molecular structure followed by calculation of the UV/Visible spectrum. At present, these steps are usually carried out

The orthogonality of Al-Salam-Carlitz polynomials for complex parameters

January 31, 2018
Author(s)
Howard Cohl, Wenqing Xu, Roberto Costas-Santos
In this contribution, we study the orthogonality conditions satisfied by Al-Salam-Carlitz polynomials $U^(a)}_n(x;q)$ when the parameters $a$ and $q$ are not necessarily real nor 'classical'. We establish orthogonality on a simple contour in the complex

SDR-Based Experiments for LTE-LAA Based Coexistence Systems with Improved Design

December 4, 2017
Author(s)
Yao Ma, Ryan T. Jacobs, Daniel G. Kuester, Jason B. Coder, William F. Young
To enhance spectrum efficiency in next generation heterogeneous wireless systems, it is important to improve shared spectrum usage between unlicensed long-term evolution (LTE) systems, such as the license assisted access (LAA), and legacy systems, such as

A Layered and Aggregated Queuing Network Simulator for Detection of Abnormalities

December 3, 2017
Author(s)
Junfei Xie, Chenyan He, Yan Wan, Kevin L. Mills, Christopher E. Dabrowski
Driven by the needs to monitor, detect, and prevent catastrophic failures for complex information systems in real-time, we develop in this paper a discrete-time queuing network simulator. The dynamic model for the simulator abstracts network dynamics by

Modeling the Internet of Things (& People): A Foundational Approach

November 16, 2017
Author(s)
Spencer J. Breiner, Eswaran Subrahmanian, Ram D. Sriram
This talk provides an overview of recent NIST work in the Internet of Things (IoT) domain in the Information Technology Laboratory. We begin with some examples and illustrations of the range of IoT systems. In addition to the obvious cyber physical aspects

The power collection method for connection relations: Meixner polynomials

November 7, 2017
Author(s)
Howard Cohl, Michael Baeder, Roberto Costas-Santos, Wenqing Xu
We use and derive connection and connection-type relations for Meixner and Krawtchouk polynomials. These relations are used to derive generalizations of generating functions for these orthogonal polynomials. The coefficients of these generalized generating

Using realistic factors to simulate catastrophic congestion events in a network

November 1, 2017
Author(s)
Kevin L. Mills, Christopher E. Dabrowski
With the rapid growth of the Internet, there has been increased interest in the use of computer models to study the dynamics of communication networks in the research literature. An important example of this has been the study of dramatic, but relatively

Evaluating the Effects of Modeling Errors for Isolated Finite 3-D Targets

October 19, 2017
Author(s)
Mark Alexander Henn, Bryan M. Barnes, Hui Zhou
Optical 3-D nanostructure metrology utilizes a model-based metrology approach to determine critical dimensions (CDs) that are well below the inspection wavelength. Our project at the National Institute of Standards and Technology is evaluating how to

MRI Birdcage RF Coil Resonance with Uncertainty and Relative Error Convergence Rates

October 4, 2017
Author(s)
Jeffrey T. Fong, Nathanael A. Heckert, James J. Filliben, Pedro V. Marcal, Robert Rainsberger, Karl F. Stupic, Stephen E. Russek
In a magnetic resonance imaging (MRI) system, it is necessary to excite the nuclei of a patient into coherent precession for imaging. This requires a coupling between the nuclei and a source of radio frequency (RF) power using a transmitter. To receive a
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