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Results for “Modeling and measurement”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Model-Free Measurement of Local Entropy Production and Extractable Work in Active Matter

Time-reversal symmetry breaking and entropy production are universal features of nonequilibrium phenomena. Despite its importance in the physics of active and living systems, the entropy production of systems with many degrees of freedom has remained of little practical significance because the high dimensionality of their state space makes it difficult to measure. Here, in this work, we introduce a local measure of entropy production and a numerical protocol to estimate it. We establish a connection between the entropy production and extractability of work in a given region of the system and show how this quantity depends crucially on the degrees of freedom being tracked. We validate our approach in theory, simulation, and experiments by considering systems of active Brownian particles undergoing motility-induced phase separation, as well as active Brownian particles and E.coli in a rectifying device in which the time-reversal asymmetry of the particle dynamics couples to spatial asymmetry to reveal its effects on a macroscopic scale.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

In situ measurement and modelling of the growth and length scale of twins in α -uranium

Twinning is an important deformation mechanism in crystalline materials. Twins nucleate, then grow, forming a discrete pattern of deformation bands with a certain thickness. The mechanism for twin growth is not completely understood. We present a simple phase field model which captures the physics of twin growth and reproduces the details observed during in situ electron backscatter diffraction experiments on α-uranium. The interaction between residual dislocations at twin interfaces and mobile dislocations in untwinned regions increases the stress needed for twin growth. This is described by a nonlocal term in the proposed constitutive equations: the nucleation stress of a twin increases proportionally to the twin phase field in a neighborhood. Competition between slip and twinning favors the nucleation of a new twin rather than the growth of a preexisting twin. The phase field model is coupled with a crystal plasticity finite element solver that includes the plastic deformation due to twinning. Simulations are able to reproduce the number of twins and their thicknesses as a function of the strain observed during in situ electron backscatter diffraction experiments. The stress-strain curve is also reproduced. This comparison allows the values of the nucleation stress and the interaction strength between residual and mobile dislocations to be found. It also gives an estimation of the density of residual dislocations that is consistent with the observed twin thickness. Finally, this model can be applied to understand microstructural effects in materials using twinning as a strengthening mechanism.

36 MATERIALS SCIENCE↗
DOE OSTI2021

The development of yield-based sooting tendency measurements and modeling to enable advanced combustion fuels

This project produced clear evidence that biofuels can reduce particulate emissions from road vehicles compared with petroleum-derived fuels. It also produced fundamental knowledge that can be used to select fuel compositions and engine designs that will maximize this benefit. This information has been disseminated through more than 20 peer-reviewed publications, more than 30 conference presentations, and 5 freely available internet databases and web tools. This project also provided educational opportunities to 17 students at the high school, undergraduate, and graduate levels.

09 BIOMASS FUELS↗
DOE OSTI2023

National Opacity Program - Tri-Lab Assessment of Measurements and Models (Milestone 7720)

Opacity-on-NIF has obtained opacity data under conditions similar to those achieved by the entirely different Opacity-on-Z platform. From low- and high-Z elements at different anchor points, rigorously compare the opacity data between the laboratories and to multiple opacity theory models. Compare and assess the data acquisition and processing methods for obtaining opacities and for measuring/inferring sample conditions. Explain, or develop hypotheses for, any discrepancies. Map progress to the National Opacity Strategy and define future directions.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Demonstration of new fracture criteria based on micro-structure and compare to empirical model and measurements

The US nuclear industry is currently exploring extending the peak rod average burnup limits above the current regulatory limit of 62 GWd/tU. A potential concern for fuel exceeding the burnup limit is the fragmentation during a temperature transient such as a loss-of-coolant accident (LOCA). In the event of cladding failure, the fragmented fuel could relocate and disperse within the reactor. The potential impact of fuel fragmentation, relocation and dispersal (FFRD) on licensing assumptions for burnup extension has focused a great amount of efforts and research on this topic.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2023

Milestone 7720: National Opacity Program - Tri-Lab Assessment of Measurements and Models

Opacity-on-NIF has obtained opacity data under conditions similar to those achieved by the entirely different Opacity-on-Z platform. From low- and high-Z elements at different anchor points, rigorously compare the opacity data between the laboratories and to multiple opacity theory models. Compare and assess the data acquisition and processing methods for obtaining opacities and for measuring/inferring sample conditions. Explain, or develop hypotheses for, any discrepancies. Map progress to the National Opacity Strategy and define future directions.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

RTN-108: Impact of CCD Non-Flatness In Rubin LSSTCam PSF Measurements and Modeling

Modeling the point-spread function (PSF) precisely is essential for achieving optimal science with the NSF-DOE Vera C. Rubin Observatory. In this work, we inspect a PSF residual pattern present in both Rubin's LSSTComCam and LSSTCam observations. We show that it is likely due to effects from CCD non-flatness and explain the physical mechanism by which height offsets could influence the PSF. Finally, we demonstrate that incorporating height information into PSF modeling greatly reduces the observed residual.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Subcell Coupling in Tandem Solar Cells: Measurements and Modeling

Closely stacking two or more photovoltaic (PV) subcells together to form tandem solar cells inevitably results in subcell coupling that is important to understand. Here we describe how this coupling can be modeled and characterized for two-, three-, and four-terminal tandems (hereafter 2T, 3T or 4T).

2T↗