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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Sensitivity of posterior parameter correlations and response parameter correlations to prior response uncertainty

The two parameters one response model of the generalized linear least squares parameter adjustment methodology was used in order to analyze the procedure of improving cross sections agreement with integral experimental results. Two extreme adjustment cases were considered. One case is using extremely accurate measured integral responses, such as k{sub eff} of Godiva or Jezebel for instance. The other one is modifying only one parameter, for instance the modification of {nu}-bar in ENDF/B-VII, in order to improve agreement of calculated responses with corresponding integral measurements results. In both cases new posterior parameters correlations are generated. The conclusion is that it is not advised to use integral measurements information in the evaluation process of a general purpose nuclear data file. (authors)

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2021

Crystal Structure of Moganite and Its Anisotropic Atomic Displacement Parameters Determined by Synchrotron X-ray Diffraction and X-ray/Neutron Pair Distribution Function Analyses

The crystal structure of moganite from the Mogán formation on Gran Canaria has been re-investigated using high-resolution synchrotron X-ray diffraction (XRD) and X-ray/neutron pair distribution function (PDF) analyses. Our study for the first time reports the anisotropic atomic displacement parameters (ADPs) of a natural moganite. Rietveld analysis of synchrotron XRD data determined the crystal structure of moganite with the space group I2/a. The refined unit-cell parameters are a = 8.7363(8), b = 4.8688(5), c = 10.7203(9) Å, and β = 90.212(4)°. The ADPs of Si and O in moganite were obtained from X-ray and neutron PDF analyses. The shapes and orientations of the anisotropic ellipsoids determined from X-ray and neutron measurements are similar. The anisotropic ellipsoids for O extend along planes perpendicular to the Si-Si axis of corner-sharing SiO4 tetrahedra, suggesting precession-like movement. Neutron PDF result confirms the occurrence of OH over some of the tetrahedral sites. We postulate that moganite nanomineral is stable with respect to quartz in hypersaline water. The ADPs of moganite show a similar trend as those of quartz determined by single-crystal XRD. In short, the combined methods can provide high-quality structural parameters of moganite nanomineral, including its ADPs and extra OH position at the surface. This approach can be used as an alternative means for solving the structures of crystals that are not large enough for single-crystal XRD measurements, such as fine-grained and nanocrystalline minerals formed in various geological environments.

58 GEOSCIENCES↗
DOE OSTI2021

A High-Throughput Method to Define Additive Manufacturing Process Parameters: Application to Haynes 282

This paper demonstrates how an analytical and experimental method can be used to rapidly define the 45 additive manufacturing settings for a new alloy where the process parameters were previously unknown. A nickel-based superalloy, Haynes 282, was chosen for the analysis. An experimental matrix of focused processing parameters was predicted with a dimensionless number and 100 samples were printed using the Selective Laser Melting technique. High-throughput measurements validated the predicted process conditions needed to achieve desired density and hardness. The whole process was completed in 16 hours. The new technique was confirmed with analytical processing maps adopted by the metal additive manufacturing community. With the predicted set of process parameters, microstructural characterizations and tensile testing were used to confirm the predictions. The resultant as-fabricated microstructures have refined length scales of both microsegregation and secondary phase distributions. As a result, the mechanical properties were comparable within the predicted processing window and exhibited high strength and high ductility.

Laser Material Processing↗
DOE OSTI2021

A Bayesian Framework for Milling Stability Prediction and Reverse Parameter Identification

This paper describes a physics-guided Bayesian framework for identifying the milling stability boundary and system parameters through iterative testing. Prior uncertainties for the parameters are identified through physical simulation and literature reviews, without physical testing of the actual milling system. Those uncertainties are then propagated to the stability map using a physics-based stability model, which is used to suggest a test point. The uncertainties are updated based on the new information acquired from the cutting test to form a new probability distribution, called the posterior. Finally, the posterior are compared to measured values for the stability boundary and system parameters to evaluate the approach. Based on experimental observations, the advantages and disadvantages of using a physics-guided model are discussed.

Cornelius, Aaron↗
DOE OSTI2013

Crystal Growth Simulations To Establish Physically Relevant Kinetic Parameters from the Empirical Kolmogorov-Johnson-Mehl-Avrami Model

A series of simulations was performed to enable interpretation of the material and physical significance of the parameters defined in the Kolmogorov, Johnson and Mehl, and Avrami (KJMA) rate expression commonly used to describe phase boundary controlled reactions of condensed matter. The parameters k, n, and t 0 are shown to be highly correlated, which if unaccounted for seriously challenge mechanistic interpretation. It is demonstrated that rate measurements exhibit an intrinsic uncertainty without precise knowledge of the location and orientation of nucleation with respect to the free volume into which it grows. More significantly, it is demonstrated that the KJMA rate constant k is highly dependent on sample size. However, under the simulated conditions of slow nucleation relative to crystal growth, sample volume and sample anisotropy correction affords a means to eliminate the experimental condition dependence of the KJMA rate constant, k, producing the material-specific parameter, the velocity of the phase boundary, v pb .

Dill, Eric D.↗
DOE OSTI2016

Parameter space of experimental chaotic circuits with high-precision control parameters

We report high-resolution measurements that experimentally confirm a spiral cascade structure and a scaling relationship of shrimps in the Chua's circuit. Circuits constructed using this component allow for a comprehensive characterization of the circuit behaviors through high resolution parameter spaces. To illustrate the power of our technological development for the creation and the study of chaotic circuits, we constructed a Chua circuit and study its high resolution parameter space. The reliability and stability of the designed component allowed us to obtain data for long periods of time (∼21 weeks), a data set from which an accurate estimation of Lyapunov exponents for the circuit characterization was possible. Moreover, this data, rigorously characterized by the Lyapunov exponents, allows us to reassure experimentally that the shrimps, stable islands embedded in a domain of chaos in the parameter spaces, can be observed in the laboratory. Finally, we confirm that their sizes decay exponentially with the period of the attractor, a result expected to be found in maps of the quadratic family.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Polarized neutron scattering study of the multiple order parameter system NdB 4 [Polarized neutron scattering study on multiple order parameter system NdB 4 ]

Neutron polarization analysis has been carried out in order to clarify the magnetic structures of multiple order parameter f-electron system NdB 4 . We confirmed the noncollinear “all-in all-out” structure (Γ 4 ) of the in-plane moment, which is in good agreement with our previous neutron powder diffraction study. We found that the magnetic moment along the c-axis m c showed diagonally antiferromagnetic structure (Γ 10 ), inconsistent with previously reported “vortex” structure (Γ 2 ). The microscopic mixture of these two structures with → q 0 =(0,0,0) appears in phase II and remains stable in phases III and IV, where an incommensurate modulation coexists. The unusual magnetic ordering is phenomenologically understood via Landau theory with the primary order parameter Γ 4 coupled with higher-order secondary order parameter Γ 10 . The magnetic moments were estimated to be 1.8 ± 0.2 and 0.2 ± 0.05μ B at T = 7.5K for Γ 4 and Γ 10 , respectively. We also found a long-period incommensurate modulation of the → q 1 =(0,0,1/2) antiferromagnetic structure of mc with the propagation → q s1 =(0.14,0.14,0.1) and → q s2 =(0.2,0,0.1) in phase III and IV, respectively. The amplitude of sinusoidal modulation was about m c =1.0 ± 0.2μ B at T=1.5 K. The local (0,0,1/2) structure consists of in-plane ferromagnetic and out-of-plane antiferromagnetic coupling of m c , opposite to the coexisting Γ 10 . The mc of Γ 10 is significantly enhanced up to 0.6μ B at T=1.5 K, which is accompanied by the incommensurate modulations. As a result, the Landau phenomenological approach indicates that the higher-order magnetic and/or multipole interactions based on the pseudoquartet f-electron state play important roles.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Inflationary features and shifts in cosmological parameters from Planck 2015 data

We explore the relationship between features in the Planck 2015 temperature and polarization data, shifts in the cosmological parameters, and features from inflation. Residuals in the temperature data at low multipole &ell;, which are responsible for the high H 0 ≈ 70 km s –1 Mpc –1 and low σ 8 $Ω^{1/2}_{m}$ values from &ell; < 1000 in power-law ΛCDM models, are better fit to inflationary features with a 1.9σ preference for running of the running of the tilt or a stronger 99% CL local significance preference for a sharp drop in power around k = 0.004 Mpc –1 in generalized slow roll and a lower H 0 ≈ 67km s –1 Mpc –1 . The same in-phase acoustic residuals at &ell; >1000 that drive the global H 0 constraints and appear as a lensing anomaly also favor running parameters which allow even lower H 0 , but not once lensing reconstruction is considered. Polarization spectra are intrinsically highly sensitive to these parameter shifts, and even more so in the Planck 2015 TE data due to an outlier at &ell; ≈ 165,which disfavors the best fit H 0 ΛCDM solution by more than 2σ, and high H 0 value at almost 3σ. Current polarization data also slightly enhance the significance of a sharp suppression of large-scale power but leave room for large improvements in the future with cosmic variance limited E-mode measurements.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

FATES Parameters and Output for Parameter Sensitivity at the Panama Barro Colorado Island Testbed

This data package contains a set of Functionally Assembled Terrestrial Ecosystem Simulator (FATES) history files and parameter values for the set of model simulations used in Koven et al. Manuscript "Benchmarking and Parameter Sensitivity of Physiological and Vegetation Dynamics using the Functionally Assembled Terrestrial Ecosystem Simulator (FATES) at Barro Colorado Island, Panama." It includes several ensembles of FATES runs, where each ensemble is comprised of a set of 576 runs that have different values of PFT traits. The ensembles include 1 PFT, 2 PFT, 3 PFT, and 10 PFT simulations. Different ensembles also have different values of disturbance and height sorting parameters, and structural differences including running FATES within different LSMs.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1976

Environmental parameters of the Tennessee River in Alabama. 2: Physical, chemical, and biological parameters

Physical, chemical and biological water quality data from five sites in the Tennessee River, two in Guntersville Reservoir and three in Wheeler Reservoir were correlated with climatological data for three annual cycles. Two of the annual cycles are for the years prior to the Browns Ferry Nuclear Power Plant operations and one is for the first 14 months of Plant operations. A comparison of the results of the annual cycles indicates that two distinct physical conditions in the reservoirs occur, one during the warm months when the reservoirs are at capacity and one during the colder winter months when the reservoirs have been drawn-down for water storage during the rainy months and for weed control. The wide variations of physical and chemical parameters to which the biological organisms are subjected on an annual basis control the biological organisms and their population levels. A comparison of the parameters of the site below the Power plant indicates that the heated effluent from the plant operating with two of the three reactors has not had any effect on the organisms at this site. Recommendations given include the development of prediction mathematical models (statistical analysis) for the physical and chemical parameters under specific climatological conditions which affect biological organisms. Tabulated data of chemical analysis of water and organism populations studied is given.

Rosing, L. M.↗
NASA NTRS1979

Comparison of stability and control parameters for a light, single-engine, high-winged aircraft using different flight test and parameter estimation techniques

The longitudinal and lateral stability and control parameters for a high wing, general aviation, airplane are examined. Estimations using flight data obtained at various flight conditions within the normal range of the aircraft are presented. The estimations techniques, an output error technique (maximum likelihood) and an equation error technique (linear regression), are presented. The longitudinal static parameters are estimated from climbing, descending, and quasi steady state flight data. The lateral excitations involve a combination of rudder and ailerons. The sensitivity of the aircraft modes of motion to variations in the parameter estimates are discussed.

Suit, W. T.↗