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Inversion of Masing models via continuous Iwan systems

Proposed for publication in the Journal of Engineering Mechanics.

Starr, Michael J.; Segalman, Daniel J.

It is shown that for any material or structural model expressible as a Masing model, there exists a unique parallel-series (displacement-based) Iwan system that characterizes that model as a function of displacement history. This poses advantages both in terms of more convenient force evaluation in arbitrary deformation histories as well as in terms of model inversion. Characterization as an Iwan system is demonstrated through the inversion of the Ramberg-Osgood model, a force(stress)-based material model that is not explicitly invertible. An implication of the inversion process is that direct, rigorous comparisons of different Masing models, regardless of the ability to invert their constitutive relationship, can be achieved through the comparison of their associated Iwan distribution densities.

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TYPE Journal Article YEAR 2007
OSTI

Practical considerations in empirical probability of detection study design

Materials Evaluation

Spencer, Floyd W.

The purposes of a POD study often go beyond the estimation of a single curve based on discontinuity size. The larger goals of a particular POD study will dictate the need for additional planning beyond just deciding on the number of discontinuities and discontinuity-free areas to be included in a test specimen set. The bigger concerns lead to implementation issues that need to be planned for and fully specified prior to the collection of data. These bigger issues have been discussed under the general program areas of experimental design, protocol development and logistic and dress rehearsal. Two different programs were also summarized. Each program led to very different experimental plans. However, the common element in these programs was the use of the POD study as the basic metric for establishing capabilities and important influencing factors. Both programs were developed under the guidelines noted and referenced. Results from these studies are discussed in more detail in Spencer (2007).

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TYPE Conference YEAR 2007
OSTIScopus

Design tools for complex dynamic security systems

Byrne, Raymond H.; Wilson, David G.; Groom, Kenneth N.; Robinett, R.D.; Harrington, John J.; Rigdon, James B.; Rohrer, Brandon R.; Laguna, Glenn A.

The development of tools for complex dynamic security systems is not a straight forward engineering task but, rather, a scientific task where discovery of new scientific principles and math is necessary. For years, scientists have observed complex behavior but have had difficulty understanding it. Prominent examples include: insect colony organization, the stock market, molecular interactions, fractals, and emergent behavior. Engineering such systems will be an even greater challenge. This report explores four tools for engineered complex dynamic security systems: Partially Observable Markov Decision Process, Percolation Theory, Graph Theory, and Exergy/Entropy Theory. Additionally, enabling hardware technology for next generation security systems are described: a 100 node wireless sensor network, unmanned ground vehicle and unmanned aerial vehicle.

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TYPE SAND Report YEAR 2007
DOIOSTI

Boolean dynamics of genetic regulatory networks inferred from microarray time series data

Bioinformatics

Martin, Shawn; Zhang, Zhaoduo Z.; Martino, Anthony M.; Faulon, Jean-Loup M.

Motivation: Methods available for the inference of genetic regulatory networks strive to produce a single network, usually by optimizing some quantity to fit the experimental observations. In this article we investigate the possibility that multiple networks can be inferred, all resulting in similar dynamics. This idea is motivated by theoretical work which suggests that biological networks are robust and adaptable to change, and that the overall behavior of a genetic regulatory network might be captured in terms of dynamical basins of attraction. Results: We have developed and implemented a method for inferring genetic regulatory networks for time series microarray data. Our method first clusters and discretizes the gene expression data using k-means and support vector regression. We then enumerate Boolean activation-inhibition networks to match the discretized data. Finally, the dynamics of the Boolean networks are examined. We have tested our method on two immunology microarray datasets: an IL-2-stimulated T cell response dataset and a LPS-stimulated macrophage response dataset. In both cases, we discovered that many networks matched the data, and that most of these networks had similar dynamics. © The Author 2007. Published by Oxford University Press. All rights reserved.

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TYPE Journal Article YEAR 2007
DOIDOIOSTIOSTIScopusScopus

High-fidelity simulation of the influence of local geometry on mixing in crosses in water distribution systems

Restoring Our Natural Habitat - Proceedings of the 2007 World Environmental and Water Resources Congress

Webb, Stephen W.

Network simulation models for water distribution systems typically assume the mixing at pipe intersections is complete and instantaneous. Recent data show that mixing may be incomplete at pipe junctions (pipe crosses and tees) under most conditions. In general, computational fluid dynamic (CFD) simulations agree with the experimental data, establishing confidence in the CFD approach for application to other situations. However, in the case of unequal inlet flow rates and equal outlet flow rates in a cross, the simulation results and experimental data show significantly different results. The reasons for this discrepancy are investigated, and a revised model is developed that is consistent with the experimental data. © 2007 ASCE.

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TYPE Conference YEAR 2007
OSTIScopus
Results 81101–81200 of 96,771
Results 81101–81200 of 96,771