Engineering topics

Hooker, J.

Publications and source records attributed to Hooker, J..

21 records · Page 2

DOE OSTI2019

Structure of C 9 through proton resonance scattering with the Texas Active Target detector

Structure of very exotic nucleus, carbon-9, has been studied using novel detector - Texas Active Target (TexAT). Carbon-9 can be produced by removing three neutrons from the stable carbon-12 isotope, which we inhale every few seconds as part of carbon-dioxide gas. The structure of this exotic carbon, carbon-9, is very different from the stable carbon (carbon-12) and much less explored due to experimental difficulties of producing it. Yet, it is important for benchmarking the contemporary, state-of-the-art theories of nuclear structure. In particular, excitation energy of the positive parity states, that indicate an onset of the sd-shell, was not known in 9C. Here, we have conclusively identified the first positive parity state in 9C. It was made possible by the new capabilities provided buy TexAT.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

NASA NTRS2013

Uncertainty in Simulating Wheat Yields Under Climate Change

Projections of climate change impacts on crop yields are inherently uncertain1. Uncertainty is often quantified when projecting future greenhouse gas emissions and their influence on climate2. However, multi-model uncertainty analysis of crop responses to climate change is rare because systematic and objective comparisons among process-based crop simulation models1,3 are difficult4. Here we present the largest standardized model intercomparison for climate change impacts so far. We found that individual crop models are able to simulate measured wheat grain yields accurately under a range of environments, particularly if the input information is sufficient. However, simulated climate change impacts vary across models owing to differences in model structures and parameter values. A greater proportion of the uncertainty in climate change impact projections was due to variations among crop models than to variations among downscaled general circulation models. Uncertainties in simulated impacts increased with CO2 concentrations and associated warming. These impact uncertainties can be reduced by improving temperature and CO2 relationships in models and better quantified through use of multi-model ensembles. Less uncertainty in describing how climate change may affect agricultural productivity will aid adaptation strategy development and policymaking.

exhaust gases↗

NASA NTRS1997

Laser Shearographic Inspection for Debonds in Sprayed On Foam Insulation (SOFI)

Preliminary results of shearographic inspections of the test panels simulating the Space Shuttle's external tank (ET) spray on foam insulation (SOFI) are presented. Debonding of SOFI may introduce flight debris that may damage the orbiter's thermal protection system (TPS) exposing the orbiter (as well as the ET) to thermal loading. It is estimated that 90 percent of the TPS damage on the orbiter's 'belly' results from debonded SOFI during ascent. A series of test panels were fabricated, with programmed debonds of different geometries and sizes, to determine the sensitivity of shearography as a function of debond size, SOFI thickness,'and vacuum excitation. Results show that a Probability of Detection (POD) of 0.95 or better can be expected for debonds with a diameter equal to the SOFI thickness as less than 0.4-psi pressure reduction. More testing will be required to validate the laser shearography imaging process for certifying its use in nondestructive evaluation (NDE) of Space Shuttle space flight components.

Adams, F. W.↗