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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 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Rapidly Approaching A Thermal Tolerance Tipping Point in the Eurasian Boreal Forest at Its Southern Margins

Extreme heat is becoming increasingly common across the boreal biome. Better quantification of vegetation physiology and thermal tolerance is needed to predict ecological responses to these events. Here we report that Larix sibirica, a foundation species across boreal Eurasia, has a low thermal tolerance of photosynthesis (Tcrit: ~40-48°C) at its southern range margin. Projections from Earth System Models (ESMs) participating in CMIP6 suggest that Larix sibirica’s leaf temperature might routinely exceed its Tcrit under high emission scenarios (SSP5-8.5 and SSP3-7.0) by 2050. Such exceedances would cause sustained damage to Larix sibirica’s photosynthetic apparatus and its ability to assimilate carbon. This work highlights that we may be rapidly approaching ecological tipping point in boreal Eurasia within the next two to three decades. It also demonstrates the urgent need to consider thermal tolerance information to forecast the terrestrial carbon cycle and presents a framework to do so.

Eurasian boreal forest↗
NASA NTRS2023

Land Surfaces at the Tipping-Point for Water and Energy Balance Coupling

The surface water and energy balances can be coupled or uncoupled depending on whether the evaporation regime is water-limited or energy-limited. As the landscape loses soil moisture during drydowns, a transition between the regimes may occur, which signifies a nonlinear change in water-energy-carbon coupling. Regions that switch often between these two regimes, that is, are dominated by neither regime, are particularly vulnerable to climate variability and change. To robustly identify these tipping points, we identify drydown events based on global soil moisture data sets from remote sensing. The event identification does not rely on precipitation information and is robust with respect to measurement noise. Then, the soil moisture thresholds delineating the evaporation regime transitions are determined by Sequential Monte Carlo Sampling and a two-stage parametrization strategy. Based on the estimated soil moisture thresholds across the globe, we estimate observation-based water availability indices which quantify the nonlinear controls of soil moisture on evaporation. This framework is tested and applied globally using Soil Moisture Active Passive soil moisture retrievals. Combined with a new tippling-point metric that describes the frequency of evaporation regime transitions, we identify regions that switch often between different evaporation regimes at the global scale. Given unit shifts in soil moisture, these regions will experience the most change in how their surface water and energy are coupled.

Jianzhi Dong↗
NASA NTRSDate not supplied

Practical Tips for Setting Up an LS-DYNA MAT_213 Analysis

Since 2012, NASA has actively contributed to the development and application of the LS-DYNA MAT_213 material model to predict responses under dynamic loading events. This presentation provides a high-level overview of MAT_213 and captures practical tips and suggestions for using it.

MAT_213↗
NASA NTRS1947

Distribution of wave drag and lift in the vicinity of wing tips at supersonic speeds

The point-source-distribution method of calculating the aerodynamic coefficients of thin wings at supersonic speeds was extended to include the effect of the region between the wing boundary and the foremost Mach wave from the wing leading edge. The effect of this region on the surface velocity potential has been determined by an equivalent function, which is evaluated over a portion of the wing surface. In this manner, the effect of angles of attack and yaw as well as the asymmetry of top and bottom wing surfaces may be calculated. As examples of the method, the pressure distribution on a thin plate wing of rectangular plan form as well as the lift and the drag coefficients as a function of Mach number, angle of attack, and aspect ratio are calculated. The equations for the surface velocity potential of several other plan forms are also included. (author)

AIRFOILS, FLAT-PLATE↗
NASA NTRS1995

Design and Process Considerations for a Tunneling Tip Accelerometer

In this paper, we discuss issues related to the fabrication of a bulk micromachined single axis accelerometer. The accelerometer is designed to have a full scale range of ten millig and a sensitivity of tens of nanog. During the process, three distinctly different die are fabricated. These are subsequently assembled using an ally bonding technique. During the bonding operation, electrical contacts are made between layers. The accelerometer is controlled by electrostatic force plates above and below the proof mass. The lower electrode has a dual role. In operation, it provides a necessary control electrode. When not in operation, it is used to clamp the proof mass and prevents its motion. Results of the fabrication process and initial testing of the clamping function are reported.

tunneling tip accelerometer, accelerometer fabrica↗
NASA NTRS2018

Data Tips: Learn How to Discover, Access and Analyze NASA GES DISC Data

At the NASA Goddard Earth Sciences Data and Information Services (GES DISC), we strive to simplify data discovery and data access to our wide range of global climate data, concentrated primarily in the areas of atmospheric composition, atmospheric dynamics, global precipitation, solar irradiance, and several modeling data sets related to land surface hydrology. To help meet user needs, we will demonstrate how you can use the GES DISC knowledge-base resources (HowTo's) and we also encourage community contributions.

data tips↗