Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Drying”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,657 records · Page 92
All sourcesNASA NTRSDOE OSTI
NASA NTRS2020

Corrigendum to: Volatiles in Lunar Felsite Clasts: Impact-related Delivery of Hydrous Material to an Ancient Dry Lunar Crust

Hydrous components were measured in nominally anhydrous minerals, primarily lunar feldspar, and reported by Simon et al. (2020). In the feldspar mineral structure, these components are contained in the form of OH, H2O, and/or NH4+molecules (Johnson, 2006 and references therein). The advantages of the ion microprobe technique employed by Simon et al. (2020) include high spatial resolution, apparent insensitivity to crystal orientation, high precision, and low detection limits, but unlike complementary spectroscopy techniques (i.e., FTIR) they preclude assignment of molecular species(Mosenfelder et al. 2015). Convention in the lunar sample community is to report major elemental abundances and hydrogen as oxides, H2O is the oxide for H. This convention was not followed by Simon et al. (2020), but rather the measured hydrogen component was reported as H to avoid the appearance of assigning the measured hydrogen concentration to a specific molecular species. The speciation of the hydrous component in terrestrial feldspars varies predominantly between OH and H2O, with no apparent correlation to feldspar composition, and only slight correlation to volcanic-to-plutonic igneous rock type (Johnson and Rossman, 2004).

J. I. Simon↗
NASA NTRS2023

A New Model of Dry Firn Densification Constrained By Continuous Strain Measurements Near South Pole

Converting measurements of ice-sheet surface elevation change to mass change requires measurements of accumulation and knowledge of the evolution of the density profile in the firn. Most firn-densification models are tuned using measured depth-density profiles, a method which is based on an assumption that the density profile in the firn is invariant through time. Here we present continuous measurements of firn-compaction rates in 12 boreholes near the South Pole over a two-year period. To our knowledge, these are the first continuous measurements of firn compaction on the Antarctic Plateau. We use the data to derive a new firn-densification algorithm framed as a constitutive relationship. We also compare our measurements to compaction rates predicted by several existing firn densification models. Results indicate that an activation energy of 60 kJ mol (−1), a value within the range used by current models, best predicts the seasonal cycle in compaction rates on the Antarctic Plateau. Our results suggest models can predict firn-compaction rates with at best 7% uncertainty and cumulative firn compaction on a two year timescale with at best 8% uncertainty.

C. Max Stevens↗