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Dunn, J.

Publications and source records attributed to Dunn, J..

7 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2018

Validation and Norms of Cognition and Spaceflight Assessments with Senior Military Leaders

Spaceflight hazards include risks to cognitive performance. NASA requires sensitive neuropsychological screening tools to determine changes to cognitive risks to crew health and performance. Currently, NASA uses WinSCAT (Spaceflight Cognitive Assessment Tool for Windows) for neurocognitive screening and to monitor the status of astronauts during spaceflight. The CognitionTest Battery was recently developed by NASA-funded researchers at UPenn as part of the Behavioral Health and Performance component of NASA Standard Measures. This research provides independently validated norms and psychometric properties to compare WinSCAT to Cognition using a military population who operates in high demand, extreme environments similar to those experienced by astronauts (deployments, isolation, extreme environments).

Williams, T. J.↗
NASA NTRS2013

Uncertainties in Atomic Data and Their Propagation Through Spectral Models. I.

We present a method for computing uncertainties in spectral models, i.e., level populations, line emissivities, and emission line ratios, based upon the propagation of uncertainties originating from atomic data.We provide analytic expressions, in the form of linear sets of algebraic equations, for the coupled uncertainties among all levels. These equations can be solved efficiently for any set of physical conditions and uncertainties in the atomic data. We illustrate our method applied to spectral models of Oiii and Fe ii and discuss the impact of the uncertainties on atomic systems under different physical conditions. As to intrinsic uncertainties in theoretical atomic data, we propose that these uncertainties can be estimated from the dispersion in the results from various independent calculations. This technique provides excellent results for the uncertainties in A-values of forbidden transitions in [Fe ii]. Key words: atomic data - atomic processes - line: formation - methods: data analysis - molecular data - molecular processes - techniques: spectroscopic

linear sets↗
NASA NTRS1983

Analysis of defect structure in silicon. Characterization of SEMIX material. Silicon sheet growth development for the large area silicon sheet task of the low-cost solar array project

Statistically significant quantitative structural imperfection measurements were made on samples from ubiquitous crystalline process (UCP) Ingot 5848 - 13C. Important correlation was obtained between defect densities, cell efficiency, and diffusion length. Grain boundary substructure displayed a strong influence on the conversion efficiency of solar cells from Semix material. Quantitative microscopy measurements gave statistically significant information compared to other microanalytical techniques. A surface preparation technique to obtain proper contrast of structural defects suitable for quantimet quantitative image analyzer (QTM) analysis was perfected and is used routinely. The relationships between hole mobility and grain boundary density was determined. Mobility was measured using the van der Pauw technique, and grain boundary density was measured using quantitative microscopy technique. Mobility was found to decrease with increasing grain boundary density.

Natesh, R.↗