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Results for “thresholds”
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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A threshold density of helium bubbles induces a ductile-to-brittle transition at a grain boundary in nickel
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Average hydrodynamic radius analysis reveals critical solvation thresholds in high-concentration lithium electrolytes
Understanding the solvation structures of lithium salts in carbonate- and ether-based electrolytes is central to explaining the exceptional stability of high-concentration electrolytes (HCEs) and localized high-concentration electrolytes (LHCEs). Conventional techniques such as vibrational spectroscopy and one-dimensional NMR provide only limited information, typically restricted to coordination ratios and ion-pair distributions, without revealing the actual size and mass of solution complexes. Here, in this study, we introduce an average hydrodynamic radius (AHR) analysis based on internally referenced DOSY NMR, which enables direct estimation of the average volume and molecular weight of lithium–solvent complexes in solution. Using LiFSI–EMC and LiFSI–EMC–TTE electrolytes, we demonstrate that the onset of effective lithium metal stabilization and aluminum corrosion suppression coincides with the formation of very large complexes, whose average volume exceeds 300 times that of free EMC molecules. This finding supports a new “blocking mechanism,” wherein bulky solvated complexes impede direct solvent access to reactive surfaces. The AHR analysis thus not only clarifies the fundamental origin of HCE and LHCE effectiveness, but also provides a broadly applicable experimental framework for probing complex solvation structures and guiding rational electrolyte design.
Measurements of a LYSO crystal array from threshold to 100 MeV
We report measurements of ten custom-made high-homogeneity LYSO crystals. The investigation is motivated by the need for a compact, high-resolution, and fast electromagnetic calorimeter for a new rare pion decay experiment. Each 2.5 x 2.5 x 18 cm 3 crystal was first characterized for general light yield properties and then its longitudinal response uniformity and energy resolution were measured using low-energy gamma sources. The ten crystals were assembled as an array and subjected to a 30–100 MeV positron beam with excellent momentum definition. The energy and timing resolutions were measured as a function of energy, and the spatial resolution was determined at 70 MeV. An additional measurement using monoenergetic 17.6 MeV gammas produced through a p-Li resonance was later made after the photosensors used in positron testing were improved. Here, as an example of the results, the energy resolution at 70 MeV of (1.52 ± 0.03) % is more than two times better than reported results using previous generation LYSO crystals.
Threshold displacement energies and primary radiation damage in AlN from molecular dynamics simulations
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Exploring S-wave threshold effects in QCD: A heavy-light approach
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Sub-threshold J/ψ and ϒ production in γA collisions
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ϕ-meson lepto-production near threshold and the strangeness D-term
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Perturbative QCD analysis of near threshold heavy quarkonium photoproduction at large momentum transfer
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Dispersive π K → π K and π π → K K ̄ amplitudes from scattering data, threshold parameters, and the lightest strange resonance κ or K 0 ∗ ( 700 )
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Temperature threshold for preferential bubble formation on grain boundaries in tungsten under in-situ helium irradiation
Understanding a material's radiation tolerance requires examining its performance under different irradiation conditions. In this work, we investigate the radiation tolerance in terms of helium bubble damage in tungsten irradiated in-situ with 16 keV helium at 1073 K and 1223 K. Damage evolution represented by helium bubble density, size and total change in volume in the grain matrices and the grain boundaries are quantified as a function of fluence. Preferential large bubble formation and a higher change in volume on the grain boundaries occurred at 1223 K, suggesting faster migration of certain helium-vacancy complexes as confirmed by a diffusion-reaction model.
Developing a surveillance system of sub-county data: Finding suitable population thresholds for geographic aggregations
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Loss-cone stabilization in rotating mirrors: thresholds and thermodynamics
In the limit of sufficiently fast rotation, rotating mirror traps are known to be stable against the loss-cone modes associated with conventional (non-rotating) mirrors. This paper calculates how quickly a mirror configuration must rotate in order for several of these modes to be stabilized (in particular, the high-frequency convective loss cone, drift cyclotron loss cone and Dory–Guest–Harris modes). Commonalities in the stabilization conditions for these modes then motivate a modified formulation of the Gardner free energy and diffusively accessible free energy to be used for systems in which the important modes have wavevectors that are orthogonal or nearly orthogonal to the magnetic field, as well as a modification to include the effects of a loss region in phase space.
Critical Percolation Threshold for Solvation-Site Connectivity in Polymer Electrolyte Mixtures
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