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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 1,387 records · Page 77
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Effect of cooler electrons on a compressive ion acoustic solitary wave in a warm ion plasma — Forbidden regions, double layers, and supersolitons

It is observed that the presence of a minority component of cooler electrons in a three component plasma plays a deterministic role in the evolution of solitary waves, double layers, or the newly discovered structures called supersolitons. The inclusion of the cooler component of electrons in a single electron plasma produces sharp increase in nonlinearity in spite of a decrease in the overall energy of the system. The effect maximizes at certain critical value of the number density of the cooler component (typically 15%–20%) giving rise to a hump in the amplitude variation profile. For larger amplitudes, the hump leads to a forbidden region in the ambient cooler electron concentration which dissociates the overall existence domain of solitary wave solutions in two distinct parameter regime. It is observed that an inclusion of the cooler component of electrons as low as < 1% affects the plasma system significantly resulting in compressive double layers. The solution is further affected by the cold to hot electron temperature ratio. In an adequately hotter bulk plasma (i.e., moderately low cold to hot electron temperature ratio), the parameter domain of compressive double layers is bounded by a sharp discontinuity in the corresponding amplitude variation profile which may lead to supersolitons.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Correlated rattling-ion origins of dielectric properties in reentrant dipole glasses BaTiO{sub 3}-BiScO{sub 3}

The local structure of the pseudo-cubic solid solution 0.6BaTiO{sub 3}-0.4BiScO{sub 3}, which exhibits reentrant dipole-glass behavior, has been determined using the Reverse Monte Carlo method to simultaneously fit (1) neutron and X-ray total scattering data (including the corresponding real-space pair-distribution functions), (2) Bi and Sc extended X-ray absorption fine structure, and (3) patterns of diffuse scattering in electron diffraction. These structural refinements revealed the multi-site probability density distributions for both Bi (14-sites) and Ti (8 sites), whereas Ba and Sc featured normal unimodal distributions. Bi atoms are displaced along both the 〈111〉 and 〈100〉 directions, while Ti atoms are shifted along 〈111〉. Correlated dynamic hopping of Bi and Ti over their corresponding split sites combined with chemical disorder is proposed as the origin of the strong frequency dispersion observed in dielectric measurements. The existence of split sites also explains the reentrant dipole-glass behavior reported for this system.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

A direct measurement of the forward shock speed in supernova remnant 0509–67.5: Constraints on the age, ambient density, shock compression factor, and electron–ion temperature equilibration

Two Hubble Space Telescope narrow-band Hα images separated in time by 1.03 years are used for a proper motion measurement of the forward shock of the LMC supernova remnant 0509–67.5, the only spectroscopically confirmed LMC remnant of Ia origin. We measure a global shock speed of 6500 ± 200 km s{sup −1} and constrain the pre-shock neutral hydrogen density to be 0.084 ± 0.003 cm{sup −3}, for a typical mean number of Hα photons produced per neutral hydrogen atom entering the forward shock. Previously published broad Hα line widths from two locations on the rim and our corresponding shock speed measurements are consistent with Balmer shock models that do not include effects of cosmic-ray acceleration. For the northeastern rim location, we limit the post-shock electron temperature to 10% of the proton temperature by also using the broad-to-narrow flux ratio. Hydrodynamic simulations for different initial ejecta density profiles constrain the age and ambient medium density; for an exponential ejecta profile and initial explosion energy of 1.4 × 10{sup 51} erg, the remnant’s age is 310{sub −30}{sup +40} years. For all evolutionary models explored, the expansion parameter falls in the range of 0.41–0.73, indicating that the remnant is still firmly in the ejecta-dominated phase of its evolution. Our measured neutral hydrogen density of the ambient medium, combined with the shocked density obtained in Williams et al., disfavors forward shock compression factors greater than ∼7.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

In Operando XRD and TXM Study on the Metastable Structure Change of NaNi 1/3 Fe 1/3 Mn 1/3 O 2 under Electrochemical Sodium-Ion Intercalation

In operando XRD and TXM-XANES approaches demonstrate that structure evolution in NaNi 1/3 Fe 1/3 Mn 1/3 O 2 during cycling follows a continuous change, and the formation of a nonequilibrium solid solution phase in the existence of two phases. Here, an O3' and P3' monoclinic phase occur, and redox couples of Ni 3+ /Ni 4+ and Fe 3+ /Fe 4+ are mainly responsible in the charge voltage range from 4.0 to 4.3 V.

36 MATERIALS SCIENCE↗