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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 1,765 records · Page 98
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Statistical features of magnetic noise in mixed-type impact fracture

We study the statistical features of magnetic noise accompanying the dynamic fracture of steel samples during mixed type fracture, where the overall ductile character of crack propagation is interrupted by a sudden brittle jump. The structure of the voltage time series is investigated by identifying discrete peaks which correspond to elementary steps of the jerky cracking process. We show that the height, duration, area, and energy of peaks have power law distributions with exponents falling close to the corresponding values of pure ductile fracture. For single peaks, a power law correlation of the height and area with the width is evidenced; however, the mixed nature of fracture gives rise to a crossover between two regimes of different exponents. The average pulse shape of micro-cracking events has a parabolic form with a right handed asymmetry similarly to quasi-static fracture propagation. The asymmetry emerges due to stress localization at the advancing crack front.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Chaotic state to self-organized critical state transition of serrated flow dynamics during brittle-to-ductile transition in metallic glass

We study serrated flow dynamics during brittle-to-ductile transition induced by tuning the sample aspect ratio in a Zr-based metallic glass. The statistical analysis reveals that the serrated flow dynamics transforms from a chaotic state characterized by Gaussian-distribution serrations corresponding to stick-slip motion of randomly generated and uncorrelated single shear band and brittle behavior, into a self-organized critical state featured by intermittent scale-free distribution of shear avalanches corresponding to a collective motion of multiple shear bands and ductile behavior. The correlation found between serrated flow dynamics and plastic deformation might shed light on the plastic deformation dynamic and mechanism in metallic glasses.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

The initial magnetic susceptibility of polydisperse ferrofluids: A comparison between experiment and theory over a wide range of concentration

Temperature dependencies of the static initial magnetic susceptibility for ferrofluids at various concentrations are studied using experiment and statistical-mechanical theories. Magnetic susceptibility measurements are carried out for twelve samples of magnetite-based fluids stabilized with oleic acid over a wide range of temperatures (210 K ≲T ≲ 390 K); all samples have the same granulometric composition but different volume ferroparticle concentrations (0.2 ≲ φ ≲ 0.5). Experimental results are analyzed using three theories: the second-order modified mean-field theory (MMF2) [A. O. Ivanov and O. B. Kuznetsova, Phys. Rev. E 64, 41405 (2001)]; its correction for polydisperse ferrofluids arising from Mayer-type cluster expansion and taking into account the first terms of the polydisperse second virial coefficient [A. O. Ivanov and E. A. Elfimova, J. Magn. Magn. Mater 374, 327 (2015)]; and a new theory based on MMF2 combined with the first terms of the polydisperse second and third virial contributions to susceptibility. It turns out that the applicability of each theory depends on the experimental sample density. If twelve ferrofluid samples are split into three groups of strong, moderate, and low concentrated fluids, the temperature dependences of the initial magnetic susceptibility in each group are very precisely described by one of the three theories mentioned above. The determination of a universal formula predicting a ferrofluid susceptibility over a broad range of concentrations and temperatures remains as a challenge.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

EVIDENCE FOR ULTRA-FAST OUTFLOWS IN RADIO-QUIET ACTIVE GALACTIC NUCLEI. II. DETAILED PHOTOIONIZATION MODELING OF Fe K-SHELL ABSORPTION LINES

X-ray absorption line spectroscopy has recently shown evidence for previously unknown Ultra-fast Outflows (UFOs) in radio-quiet active galactic nuclei (AGNs). These have been detected essentially through blueshifted Fe XXV/XXVI K-shell transitions. In the previous paper of this series we defined UFOs as those highly ionized absorbers with an outflow velocity higher than 10,000 km s{sup -1} and assessed the statistical significance of the associated blueshifted absorption lines in a large sample of 42 local radio-quiet AGNs observed with XMM-Newton. The present paper is an extension of that work. First, we report a detailed curve of growth analysis of the main Fe XXV/XXVI transitions in photoionized plasmas. Then, we estimate an average spectral energy distribution for the sample sources and directly model the Fe K absorbers in the XMM-Newton spectra with the detailed Xstar photoionization code. We confirm that the frequency of sources in the radio-quiet sample showing UFOs is >35% and that the majority of the Fe K absorbers are indeed associated with UFOs. The outflow velocity distribution spans from {approx}10,000 km s{sup -1} ({approx}0.03c) up to {approx}100,000 km s{sup -1} ({approx}0.3c), with a peak and mean value of {approx}42,000 km s{sup -1} ({approx}0.14c). The ionization parameter is very high and in the range log {xi} {approx} 3-6 erg s{sup -1} cm, with a mean value of log {xi} {approx} 4.2 erg s{sup -1} cm. The associated column densities are also large, in the range N{sub H} {approx} 10{sup 22}-10{sup 24} cm{sup -2}, with a mean value of N{sub H} {approx} 10{sup 23} cm{sup -2}. We discuss and estimate how selection effects, such as those related to the limited instrumental sensitivity at energies above 7 keV, may hamper the detection of even higher velocities and higher ionization absorbers. We argue that, overall, these results point to the presence of extremely ionized and possibly almost Compton-thick outflowing material in the innermost regions of AGNs. This also suggests that UFOs may potentially play a significant role in the expected cosmological feedback from AGNs and their study can provide important clues on the connection between accretion disks, winds, and jets.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

PROFILES OF DARK MATTER VELOCITY ANISOTROPY IN SIMULATED CLUSTERS

We report statistical results for dark matter (DM) velocity anisotropy, {beta}, from a sample of some 6000 cluster-size halos (at redshift zero) identified in a {Lambda}CDM hydrodynamical adaptive mesh refinement simulation performed with the ENZO code. These include profiles of {beta} in clusters with different masses, relaxation states, and at several redshifts, modeled both as spherical and triaxial DM configurations. Specifically, although we find a large scatter in the DM velocity anisotropy profiles of different halos (across elliptical shells extending to at least {approx}1.5r{sub vir}), universal patterns are found when these are averaged over halo mass, redshift, and relaxation stage. These are characterized by a very small velocity anisotropy at the halo center, increasing outward to {approx}0.27 and leveling off at {approx}0.2r{sub vir}. Indirect measurements of the DM velocity anisotropy fall on the upper end of the theoretically expected range. Though measured indirectly, the estimations are derived by using two different surrogate measurements-X-ray and galaxy dynamics. Current estimates of the DM velocity anisotropy are based on a very small cluster sample. Increasing this sample will allow theoretical predictions to be tested, including the speculation that the decay of DM particles results in a large velocity boost. We also find, in accord with previous works, that halos are triaxial and likely to be more prolate when unrelaxed, whereas relaxed halos are more likely to be oblate. Our analysis does not indicate that there is significant correlation (found in some previous studies) between the radial density slope, {gamma}, and {beta} at large radii, 0.3 r{sub vir} < r < r{sub vir}.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

REVISITING THE SCALING RELATIONS OF BLACK HOLE MASSES AND HOST GALAXY PROPERTIES

New kinematic data and modeling efforts in the past few years have substantially expanded and revised dynamical measurements of black hole masses (M {sub .}) at the centers of nearby galaxies. Here we compile an updated sample of 72 black holes and their host galaxies, and present revised scaling relations between M {sub .} and stellar velocity dispersion ({sigma}), V-band luminosity (L), and bulge stellar mass (M {sub bulge}), for different galaxy subsamples. Our best-fitting power-law relations for the full galaxy sample are log{sub 10}(M {sub .}) = 8.32 + 5.64log{sub 10}({sigma}/200 km s{sup -1}), log{sub 10}(M {sub .}) = 9.23 + 1.11log{sub 10}(L/10{sup 11} L {sub Sun }), and log{sub 10}(M {sub .}) = 8.46 + 1.05log{sub 10}(M {sub bulge}/10{sup 11} M {sub Sun }). A log-quadratic fit to the M {sub .}-{sigma} relation with an additional term of {beta}{sub 2} [log{sub 10}({sigma}/200 km s{sup -1})]{sup 2} gives {beta}{sub 2} = 1.68 {+-} 1.82 and does not decrease the intrinsic scatter in M {sub .}. Including 92 additional upper limits on M {sub .} does not change the slope of the M {sub .}-{sigma} relation. When the early- and late-type galaxies are fit separately, we obtain similar slopes of 5.20 and 5.06 for the M {sub .}-{sigma} relation but significantly different intercepts-M {sub .} in early-type galaxies are about two times higher than in late types at a given sigma. Within early-type galaxies, our fits to M {sub .}({sigma}) give M {sub .} that is about two times higher in galaxies with central core profiles than those with central power-law profiles. Our M {sub .}-L and M {sub .}-M {sub bulge} relations for early-type galaxies are similar to those from earlier compilations, and core and power-law galaxies yield similar L- and M {sub bulge}-based predictions for M {sub .}. When the conventional quadrature method is used to determine the intrinsic scatter in M {sub .}, our data set shows weak evidence for increased scatter at M {sub bulge} < 10{sup 11} M {sub Sun} or L{sub V} < 10{sup 10.3} L {sub Sun }, while the scatter stays constant for 10{sup 11} < M {sub bulge} < 10{sup 12.3} M {sub Sun} and 10{sup 10.3} < L{sub V} < 10{sup 11.5} L {sub Sun }. A Bayesian analysis indicates that a larger sample of M {sub .} measurements would be needed to detect any statistically significant trend in the scatter with galaxy properties.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Analytic results for scalar-mediated Higgs boson production in association with two jets

Abstract We present compact analytic formulae for all one-loop amplitudes representing the production of a Higgs boson in association with two jets, mediated by a colour triplet scalar particle. Many of the integral coefficients present for scalar mediators are identical to the case when a massive fermion circulates in the loop, reflecting a close relationship between the two theories. The calculation is used to study Higgs boson production in association with two jets in a simplified supersymmetry (SUSY) scenario in which the dominant additional contributions arise from loops of top squarks. The results presented here facilitate an indirect search for top squarks in this channel, by a precision measurement of the corresponding cross section. However, we find that the potential for improved discrimination between the Standard Model and SUSY cases suggested by the pattern of results in the one- and two-jet samples is unlikely to be realized due to the loss in statistical power compared to an inclusive analysis.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

Wavelet flow for extragalactic foreground simulations

Extragalactic foregrounds in cosmic microwave background (CMB) observations are both a source of cosmological and astrophysical information and a nuisance to the CMB. Effective field-level modeling that captures their non-Gaussian statistical distributions is increasingly important for optimal information extraction, particularly given the low-noise observations from current and upcoming experiments. Here, we explore the use of Wavelet Flow (WF) models to tackle the novel task of modeling the field-level probability distributions of multi-component CMB secondaries and foregrounds. Specifically, we jointly train correlated CMB lensing convergence (κ) and cosmic infrared background (CIB) maps with a WF model and obtain a network that statistically recovers the input to high accuracy — the trained network generates samples of κ and CIB fields whose average power spectra are within a few percent of the inputs across all scales, and whose Minkowski functionals are similarly accurate compared to the inputs. Leveraging the multiscale architecture of these models, we fine-tune both the model parameters and the priors at each scale independently, optimizing performance across different resolutions. These results demonstrate that WF models can accurately simulate correlated components of CMB secondaries, supporting improved analysis of cosmological data. Our code and trained models can be found on this GitHub repo.

cosmological simulations↗
DOE OSTI2020

Unified bulk semiclassical theory for intrinsic thermal transport and magnetization currents

In this work, we reveal the unexpected role of the material inhomogeneity in unifying the formulation of intrinsic thermal and thermoelectric transport as well as magnetization currents. The smooth inhomogeneity leads to the position dependent local band dispersion and phase-space Berry curvature, enabling a general and rapid access to transport and magnetization currents displaying the momentum-space Berry curvature physics. Our theory does not invoke the boundary current, the thermodynamic approach to magnetization or any mechanical counterpart of statistical forces. By introducing a fictitious inhomogeneity, it applies to homogeneous samples as well, promoting the inhomogeneity to be a basic trick in semiclassical transport theories. Such a trick works regardless of the driving force of transport, e.g., temperature gradient, in contrast to the trick of fictitious gravitational field in quantum transport theories. We thus include more general mechanical driving forces and establish the Mott relation between the resulting transport thermal and electric currents, whereas this relation for these two currents was previously only known when an electric field is the driving force.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Lensing covariance on cut sky and SPT - P l a n c k lensing tensions

We investigate correlations induced by gravitational lensing on simulated cosmic microwave background data of experiments with an incomplete sky coverage and their effect on inferences from the South Pole Telescope (SPT) data. These correlations agree well with the theoretical expectations, given by the sum of supersample and intrasample lensing terms, with only a typically negligible ~5 % discrepancy in the amplitude of the supersample lensing effect. Including these effects we find that lensing constraints are in 3.0 σ or 2.1 σ tension between the SPT polarization measurements and Planck temperature or lensing reconstruction constraints respectively. If the lensing-induced covariance effects are neglected, the significance of these tensions increases to 3.5 σ or 2.5 σ . Using the standard scaling parameter AL substantially underestimates the significance of the tension once other parameters are marginalized over. By parameterizing the supersample lensing through the mean convergence in the SPT footprint, we find a hint of underdensity in the SPT region. We also constrain extra sharpening of the cosmic microwave background acoustic peaks due to missing smoothing of the peaks by supersample lenses at a level that is much smaller than the lens sample variance. Finally, we extend the usual “shift in the means” statistic for evaluating tensions to non-Gaussian posteriors, generalize an approach to extract correlation modes from noisy simulated covariance matrices, and present a treatment of correlation modes not as data covariances but as auxiliary model parameters.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

SU-E-T-79: A Study of the Effect of Clinical Tumor Volume Displacement On the Dosage of Post Modified Radical Mastectomy Intensity-Modulated Radiation Therapy Plans for Left-Sided Breast Cancer

Purpose: To explore the effect of clinical tumor volume (CTV) displacement on the dosage of intensity-modulated radiation therapy (IMRT) plans for left-sided breast cancer after modified radical mastectomy. Methods: We created 2 sets of IMRT plans based on PTV0.5 and PTV0.7 (with CTV displacement of 0.5cm and 0.7cm respectively) for each of the ten consecutive left-sided breast cancer patients after modified radical mastectomy, and compared the difference in PTV coverage and organ at risk (OAR) sparing between the two groups. And then, we compared the difference in PTV coverage in IMRT plans based on PTV0.5 between the group with properly estimated CTV displacement (presuming the actual CTV displacement was 0.5cm) and the one with underestimated CTV displacement (presuming the actual CTV displacement was 0.7cm). The difference in results between the corresponding two groups was compared using paired-sample t-test. P values less than 0.05 were considered statistically significant. Results: IMRT plans derived from PTV0.5 had more homogenous PTV coverage, and less heart, left lung, right breast, right lung, left humeral head and B-P radiation exposure, as well as less total Mu as compared with the ones stemmed from PTV0.7 (all p<0.05). IMRT plans with appropriate estimation of CTV displacement had better PTV coverage compared with the ones with underestimated CTV displacement (all p<0.01). Conclusion: The IMRT plans with smaller CTV displacement in post modified radical mastectomy radiotherapy for left-sided breast cancer has dosimetrical advantages over the ones with larger CTV displacement. Underestimation of CTV displacement can lead to significant reduction of PTV coverage. Individually quantifying and minimizing CTV displacement can significantly improve PTV coverage and OAR (including heart and left lung) sparing. This work was supported by the Medical Scientific Research Foundation of Guangdong Procvince (A2014455 to Changchun Ma)

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

2D-DIC Challenge MATLAB Analysis Code v. 1.0

This code replicates the analysis completed in the published article (see reference below) for the 2D-DIC Challenge (https://sem.org/dic-challenge/), conducted under the auspices of the Society for Experimental Mechanics (SEM). The purpose of the DIC Challenge is to provide a set of vetted and standard images, which all users and developers of Digital Image Correlation (DIC) software can use -DIC Challenge results from Sample 14 and Sample 15 of the DIC-Challenge images, and computes various statistics on the data, such as the noise, bias, and spatial resolution. P.L. Reu, E. Toussaint, E. Jones, H.A. Bruck, M. Iadicola, R. Balcaen, D.Z. Turner, T. Siebert, P. Lava, M. Simonsen (2018) Exp. Mech. 58(7):1067-1099, https://doi.org/10.1007/s11340-017-0349-0.

Jones, Elizabeth↗
DOE OSTI2021

Models for synthetic data generation

The software includes a suite of probabilistic statistical/machine learning models that can generate discrete synthetic data. Each model is trained on a set of real (private) data and then it can be used to generate synthetic but statistically similar data. Once ready, the model can generate as many samples as we want. Finally, in addition to the actual models, the software includes code to process data, evaluate results (based on cross validation), and produce reports.

De Oliveira Sales, Ana Paula↗
DOE OSTI2024

Data and scripts associated with “Riverine dissolved organic matter transformations increase with watershed area, water residence time, and Damköhler numbers in nested watersheds” (v2)

This data package is associated with the publication “Riverine dissolved organic matter transformations increase with watershed area, water residence time, and Damköhler numbers in nested watersheds” submitted to Biogeochemistry by Ryan et al., 2024 (DOI: https://doi.org/10.1007/s10533-024-01169-5). This study aims to investigate fundamental and transferable drivers of dissolved organic matter (DOM) diversity across five nested watersheds within the contiguous United States. DOM diversity was explored using ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). The samples and the unprocessed FTICR-MS data used in this study are publicly available on the Environmental System Science Data Infrastructure for a Virtual Ecosystem (ESS-DIVE) data repository (see DOIs below). The data for the Willamette, Gunnison, Connecticut, and Deschutes basins were collected as part of a collaboration between the Watershed Rules of Life (WROL) project and Worldwide Hydrobiogeochemistry Observation Network for Dynamic River Systems (WHONDRS). The data for the Yakima River basin (YRB) was collected by the PNNL River Corridor SFA. The raw, unprocessed FTICR-MS data with additional (meta)data can be found at doi:10.15485/1895159 for WROL samples and doi:10.15485/1898912 for YRB samples. This data package contains the processed data used in the associated manuscript. This package also contains ancillary geospatial, hydrological, and geochemical information that supports the interpretation of the FTICR-MS data within Ryan et al., 2024. This data package is associated with the GitHub repository found at https://github.com/WHONDRS-Hub/rcsfa-RC4-WROL-YRB_DOM_Diversity. This data package was originally published August 2024. It was updated January 2025 (modified files). See the change history in the readme more details. At the directory level, the data package is comprised of three folders: (1) data, (2) output, and (3) src; and five additional files including the data dictionary (file ending in "_dd.csv”) and file-level metadata (file ending in “_flmd.csv”). The “src” folder contains the scripts used to process the FTICR data, conduct the analyses, and produce the manuscript figures. The inputs for these scripts are in the “data” folder and the returned outputs in the “output” folder. Inputs include temporal and spatial metadata associated with the sampling efforts, processed FTICR data, and total and normalized putative biochemical transformations per sample. Outputs include cleaned and combined data presented as tables, descriptive statistics, and plots. The file-level metadata file lists all files contained in this data package and descriptions for each. The data dictionary describes the units and definitions for each tabular data column or row header.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Hierarchical Linear Regression (Rev. 1)

We describe an algorithm for making inferences in a hierarchical linear model. The model allows different slopes and intercepts for different groups, and ties together the different slopes by representing them as samples from a higher level distribution. (The intercepts are treated as statistically independent.) Our model and code permit many options for the variance of this hierarchical distribution for the slopes, including gamma distributions on the precision, t-distributions on the standard error, pooled slopes (all equal), and independent slopes. The algorithm is described in the paper; an implementation of the algorithm in R is available on request.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2018

Escaping Events at the NOvA Far Detector

aThe NuMI Off-axis $\nu_e$ Appearance (NOvA) experiment studies neutrino oscillations in the NuMI (Neutrinos at the Main Injector) beam. The goal of the experiment is to determine the mass hierarchy and measure $\delta_{CP}$, however it is also sensitive to $\sin\theta_{23}$, and $\Delta m^2_{32}$. The present work tries to improve experimental sensitivity to the oscillation parameters by considering neutrino events which are discarded by the previous analysis - escaping events. The biggest issues with the escaping sample are significant cosmic background and correct energy estimation. Both issues were addressed and inclusion of escaping sample to the final fit led to an effective increase of statistics by 4% with best- fit measurements of $\sin\theta^2_{23} = 0.504$ and $\Delta m^2_{32} = 2.45 \times 10^{-3}$ eV$^2$.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Bayesian Optimal Sensor Augmentation Via Estimated Mutual Information

We consider the problem of designing a sensor network to most efficiently locate the source of a seismic event. The left panel of Figure 1 shows 982 possible sensor locations in a region of interest. The objective is to infer the unknown location of an earthquake, indicated by the gold dot for illustration purposes. Assume that three sensors have already been placed for data collection. Travel times of the P-wave from the source to the three sensors are observed and used to infer the unknown source location via a Bayesian statistical model described subsequently. The right panel of Figure 1 shows samples from the resulting posterior distribution for source location along with a posterior estimate of this location.

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

Galaxy Clustering with LSST: Effects of Number Count Bias from Blending

The Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) will survey the southern sky to create the largest galaxy catalog to date, and its statistical power demands an improved understanding of systematic effects such as source overlaps, also known as blending. In this work we study how blending introduces a bias in the number counts of galaxies (instead of the flux and colors), and how it propagates into galaxy clustering statistics. We use the 300 deg 2 DC2 image simulation and its resulting galaxy catalog (LSST Dark Energy Science Collaboration et al. 2021) to carry out this study. We find that, for a LSST Year 1 (Y1)-like cosmological analyses, the number count bias due to blending leads to small but statistically significant differences in mean redshift measurements when comparing an observed sample to an unblended calibration sample. In the two-point correlation function, blending causes differences greater than 3σ on scales below approximately 10', but large scales are unaffected. We fit Ω m and linear galaxy bias in a Bayesian cosmological analysis and find that the recovered parameters from this limited area sample, with the LSST Y1 scale cuts, are largely unaffected by blending. Our main results hold when considering photometric redshift and a LSST Year 5 (Y5)-like sample.

79 ASTRONOMY AND ASTROPHYSICS↗