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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Validation of 3D cryoEM single-particle reconstruction correctness and handedness with Ewald's sphere correction

The correct description of quantum scattering places the observed scattering contributions on the Ewald's sphere and its Friedel mate copy. In electron microscopy, due to the large radius of the Ewald's sphere, these scattering contributions are typically merged during data analysis. We present an approach that separates and factorizes those contributions into real and imaginary components of the image. When an inverted solution is calculated, the map derived from the real component of the image generates an inverted solution, while the map derived from the imaginary component of the image generates an inverted and sign-flipped solution. Therefore, the sign of correlation between reconstructions derived from the real and imaginary components provides the automatic determination of handedness and additional validation for the quality of 3D reconstructions. The factorization and its implementation are robust enough to be routinely used in single-particle reconstructions, even at resolutions below the limit where the curvature of the Ewald's sphere affects the overall signal-to-noise ratio.

Chemistry↗
DOE OSTI2017

Simulation–Extrapolation for Bias Correction with Exposure Uncertainty in Radiation Risk Analysis Utilizing Grouped Data

Summary In observational epidemiological studies, the exposure that is received by an individual often cannot be precisely observed, resulting in measurement error, and a common approach to dealing with measurement error is regression calibration (RC). Use of RC, which requires assumptions about the distribution of unknown error-free (true) variables, leads to concern about the possibility of bias due to misspecification of that distribution. The simulation–extrapolation (SIMEX) method, in contrast, does not require a distributional assumption. However, analyses of large cohorts may be performed by using grouped or person-year data, and application of SIMEX to grouped data is not straightforward, particularly when there is a mixture of classical and Berkson measurement errors. We compared RC and SIMEX with grouped data analyses to assess robustness of the RC method to misspecification of the true dose distribution. We also applied SIMEX assuming mixtures of classical and Berkson errors and compared the results with those obtained by using RC for classical error only. SIMEX had less bias than RC and performed well regardless of the true dose distribution, whereas RC based on a misspecified true dose distribution showed greater bias than when based on the correctly specified true dose distribution.

Misumi, Munechika↗
DOE OSTI2016

Corrective Action Plan for Corrective Action Unit 568: Area 3 Plutonium Dispersion Sites Nevada National Security Site, Nevada, Revision 0 with ROTC 1

The purpose of this CAP is to provide the plan for implementation of the recommended corrective action alternatives (CAAs) for CAU 568. Site characterization activities were performed in 2014, and the results are presented in Appendix A of the CAU 568 CADD. The CAAs were recommended in the CADD. The scope of work required to implement the recommended CAAs of closure in place and clean closure at 11 of the 14 CASs includes the following: The installation of physical barriers over the nine safety experiment ground zeroes to cover contamination at CASs 03-23-20 (Otero), 03-23-23 (San Juan and Pascal-C), 03-23-31 (Pascal-B, Luna, Colfax), 03-23-32 (Pascal-A), 03-23-33 (Valencia), and 03-23-34 (Chipmunk); the characterization and removal of three soil and debris piles at CAS 03-08-04, and one HCA soil pile at CAS 03-23-30; the removal of three steel well head covers (PSM) from CASs 03-23-20 (Otero), 03-23-31 (Luna), and 03-23-33 (Valencia); the removal of soil and lead PSM from two locations at CAS 03-26-04; Implementation of FFACO use restrictions at nine safety experiment ground zeroes at CASs 03-23-20, 03-23-23, 03-23-31, 03-23-32, 03-23-33, and 03-23-34; the steel well head cover at CAS 03-23-23; the areas meeting HCA conditions at CASs 03-23-19 and 03-23-31; and the Boomer crater area at CAS 03-45-01. The FFACO use restriction boundaries will be presented in the CAU 568 closure report.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1980

MRS proof-of-concept on atmospheric corrections. Atmospheric corrections using an orbital pointable imaging system

The feasibility of using a pointable imager to determine atmospheric parameters was studied. In particular the determination of the atmospheric extinction coefficient and the path radiance, the two quantities that have to be known in order to correct spectral signatures for atmospheric effects, was simulated. The study included the consideration of the geometry of ground irradiance and observation conditions for a pointable imager in a LANDSAT orbit as a function of time of year. A simulation study was conducted on the sensitivity of scene classification accuracy to changes in atmospheric condition. A two wavelength and a nonlinear regression method for determining the required atmospheric parameters were investigated. The results indicate the feasibility of using a pointable imaging system (1) for the determination of the atmospheric parameters required to improve classification accuracies in urban-rural transition zones and to apply in studies of bi-directional reflectance distribution function data and polarization effects; and (2) for the determination of the spectral reflectances of ground features.

Slater, P. N.↗
NASA NTRS1994

Tropospheric corrections to GPS measurements using locally measured meteorological parameters compared with general tropospheric corrections

At the Technical University Graz (TUG), Austria, the Global Positioning System (GPS) has been used for time transfer purposes since the early 80's and from that time on local meteorological parameters have been recorded together with each measurement (satellite track). The paper compares the tropospheric corrections (delays) obtained from models usually employed in GPS receivers and those using locally measured meteorological parameters.

Kirchner, D.↗