Search NASA⌕ Search

SEARCH · Search NASA

Results for “structural evolution”

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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Structural evolution of Arsia Mons, Pavonis Mons, and Ascreus Mons Tharsis region of Mars

Analysis of Viking Orbiter data suggests that Arsia Mons, Pavonis Mons, and Ascreus Mons, three large shield volcanoes of the Tharsis volcanoes of Mars, have had similar evolutionary trends. Arsia Mons appears to have developed in the following sequence: (1) construction of a main shield volcano, (2) outbreak of parasitic eruption centers on the northeast and southwest flanks, (3) volcano-tectonic subsidence of the summit and formation of concentric fractures and grabens, possibly by evacuation of an underlying magma chamber during eruption of copious lavas from parasitic eruption centers on the northeast and southwest flanks, and (4) continued volcanism along a fissure or rift bisecting the main shield, resulting in flooding of the floor of the volcano-tectonic depression and inundation of the northeast and southwest flanks by voluminous lavas locally forming parasitic shields. In terms of this sequence Pavonis Mons has developed to stage (3) and Ascreus Mons has evolved to stage (2). This interpretation is supported by crater frequency-diameter distributions in the 0.1- to 3.0-km diameter range.

Crumpler, L. S.↗
NASA NTRS1983

Stratigraphy and structural evolution of southern Mare Serenitatis - A reinterpretation based on Apollo Lunar Sounder Experiment data

Two subsurface reflecting horizons have been detected by the Apollo Lunar Sounder Experiment (ALSE) in the southern Mare Serenitatis which appear to be regolith layers more than 2 m thick, and are correlated with major stratigraphic boundaries in the southeastern Mare Serenitatis. The present stratigraphic boundaries in the southeastern Mare Serenitatis. The present analysis implies that the lower horizon represents the interface between the earliest mare unit and the modified Serenitatis basin material below. The depth of volcanic fill within Serenitatis is highly variable, with an average thickness of mare basalts under the ALSE ground track of 1.6 km. Comparisons with the Orientale basin topography suggests that a major increaae in load thickness could occur a few km basinward of the innermost extent of the traverse. The history of volcanic infilling of Mare Serenitatis was characterized by three major episodes of volcanism.

Sharpton, V. L.↗
NASA NTRS2015

Structural Evolution of a Warm Frontal Precipitation Band During GCPEx

A warm frontal precipitation band developed over a few hours 50-100 km to the north of a surface warm front. The 3-km WRF was able to realistically simulate band development, although the model is somewhat too weak. Band genesis was associated with weak frontogenesis (deformation) in the presence of weak potential and conditional instability feeding into the band region, while it was closer to moist neutral within the band. As the band matured, frontogenesis increased, while the stability gradually increased in the banding region. Cloud top generating cells were prevalent, but not in WRF (too stable). The band decayed as the stability increased upstream and the frontogenesis (deformation) with the warm front weakened. The WRF may have been too weak and short-lived with the band because too stable and forcing too weak (some micro issues as well).

PMM↗
DOE OSTI2022

Dynamic Measurements of the Structural Evolution of Material Defects at the Mesoscale

This is a technical report to be published as part of the FY2021 annual overview package. We have designed experiments and developed analytical methods using images from x-ray and electron microscopy in order to quantify the behavior of crystal dislocation defects at their native nanometer-length and micro-length scales. The results of these analyses are used to directly inform theoretical physics models and guide interpretation of dark field x-ray microscopy (DFXM) images that offer spatial resolution surpassing the resolution of beamline optics. Additionally, we developed new analytical methods to automate the alignment of optics hardware used in both synchrotron and x-ray free electron laser beamline facilities. The tools and workflows developed for this project are now being deployed as proof-of-concept in reaction history analysis (RHA) for future programmatic integration.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Evolution of Structural Order and Magnetic Anisotropy in Yb 0.5 (Co 1– x Fe x ) 3 Ge 3 through Doping of a Kagome Lattice

Kagome materials provide fruitful grounds for exploring the intersection of topology and magnetism. In this article, the single crystal growth of Yb 0.5 (Co 1–x Fe x ) 3 Ge 3 (x = 0.00, 0.25, 0.50, 0.75, and 1.00) is reported. As Fe is substituted into the Co-containing kagome net, the structure transforms from the disordered Y 0.5 Co 3 Ge 3 /CoSn-type hybrid structure to the ordered HfFe 6 Ge 6 -type structure. Diffusive scattering is observed in all doped concentrations that eventually converge to a single reflection in the Fe end member, ultimately doubling the unit cell along the c-axis. Anisotropic magnetic measurements were performed to evaluate how the magnetism of the kagome lattice is influenced by Fe substitution. Magnetic interactions are primarily observed along the c-axis. Additionally, a reorientation of the magnetic easy axis is observed with increasing Fe incorporation, highlighting how the magnetism of this material can be chemically tuned. Resistivity with unusual behavior observed in the doped compositions is also reported. Furthermore, the rationale behind the structural evolution from disordered to ordered is discussed.

36 MATERIALS SCIENCE↗
NASA NTRS1990

Structure and evolution of irradiated accretion disks. I - Static thermal equilibrium structure. II - Dynamical evolution of a thermally unstable torus

The thermal equilibrum structure and dynamical behavior of externally irradiated accretion disks are investigated. For radiative disks only the surface layer is heated, while for convective disks the heat penetrates deeply into the disk. For sufficiently strong radiation and given irradiation flux F(irr), the disk is completely stabilized against thermal instabilities of the sort invoked to explain dwarf novae. For moderately strong irradiation there is still an unstable branch in the thermal equilibrium curve. In typical soft X-ray transients, the disk is unstable against the dwarf-nova type instability. Fixed F(irr) on accretion disk annuli reduces the amplitude and the quiescent times and increases the outburst duration of the resultant light curves. Varying F(irr) in proportion to the mass accretion rate at the disks's inner edge results in light curves with a plateau in the decay from outbursts. In the case when irradiation is suddenly switched on, a temperature inversion results which leads to the formation of an accretion corona.

Tuchman, Y.↗
NASA NTRS1977

Interstellar bubbles. II - Structure and evolution

The detailed structure of the interaction of a strong stellar wind with the interstellar medium is presented. First, an adiabatic similarity solution is given which is applicable at early times. Second, a similarity solution is derived which includes the effects of thermal conduction between the hot (about 1 million K) interior and the cold shell of swept-up interstellar matter. This solution is then modified to include the effects of radiative energy losses. The evolution of an interstellar bubble is calculated, including the radiative losses. The quantitative results for the outer-shell radius and velocity and the column density of highly ionized species such as O VI are within a factor 2 of the approximate results of Castor, McCray, and Weaver (1975). The effect of stellar motion on the structure of a bubble, the hydrodynamic stability of the outer shell, and the observable properties of the hot region and the outer shell are discussed.

Weaver, R.↗
NASA NTRS1976

The relativistic equations of stellar structure and evolution. Stars with degenerate neutron cores. 1: Structure of equilibrium models

The general relativistic equations of stellar structure and evolution are reformulated in a notation which makes easy contact with Newtonian theory. Also, a general relativistic version of the mixing-length formalism for convection is presented. Finally, it is argued that in previous work on spherical systems general relativity theorists have identified the wrong quantity as "total mass-energy inside radius r."

Thorne, K. S.↗
DOE OSTI2022

Evolution of structure and transport properties of the Ba 8 Cu 16 P 30 clathrate-I framework with the introduction of Ga

Two type-I clathrates were synthesized by introducing Ga into the framework of the Ba 8 Cu 16 P 30 type-I clathrate. The introduction of minute amounts of Ga, 1.9% Ga/M total (where M total = Cu + Ga), resulted in the disturbance of the completely ordered Pbcn superstructure of Ba 8 Cu 16 P 30 . Ba 8 Cu 15.43(2) Ga 0.3 P 30.26(3) crystallizes in a partially ordered orthorhombic Pmna clathrate-I superstructure with five out of 15 framework sites being jointly occupied by metal+phosphorus. Increasing the Ga content resulted in all framework sites being occupied by metal + phosphorus in the archetype cubic Pm n clathrate-I crystal structure of Ba 8 Cu 14.5(3) Ga 1.3 P 30.2(4) with 8.2% Ga/M total . A combination of energy dispersive x-ray spectroscopy, inductively coupled plasma mass spectroscopy, and single crystal x-ray diffraction was used to determine the structures alongside the compositions. The positional disorder was verified by 31 P solid state NMR spectroscopy. Characterization of the transport properties indicated that the Ga-substituted samples exhibit higher Seebeck coefficients and electrical resistivities compared to its pristine counterpart, in line with the expected reduction of the hole concentration due to Ga/Cu substitution. Moderate improvements in the thermoelectric power factor and overall figure-of-merit were observed for samples with 6.9% and 3.8% Ga/M total as compared to those for the pristine Ba 8 Cu 16 P 30 clathrate. Finally, band structure calculations shed light on how Ga substitution affects the electronic structure and thermoelectric properties of studied clathrates.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2003

NASA Education Forum at SAO on the Structure and Evolution of the Universe

NASA's Structure and Evolution of the Universe (SEU) science theme offers an unparalleled opportunity to capture the public's imagination and inspire the next generation of scientific explorers-the generation that will determine America's lead in science and technology in the 21st century. The missions and research programs of SEU science are transporting the public to some of the universe's most exotic destinations: the beginning of time, the edge of space at the entrance to a black hole, and the great cycles of matter and energy that have slowly brought life to the universe. NASA's Office of Space Science (OSS) has put in place an Education and Public Outreach (EPO) initiative designed to do just that. Spanning all of NASA's OSS science themes, the initiative is a far-reaching partnership with the education community. As a result, NASA space science now reaches every avenue of education-from the nation's schools, science museums and planetariums, to libraries, community groups and after-school programs. As a partner in this enterprise, the,SEU Forum has successfully brought SEU science to a large and diverse audience. But this is an ongoing process, and much still needs to be done. Working with our colleagues in the OSS Support Network, and with our partners in the space science and education communities, we look forward to ensuring that the public supports and participates in the great explorations of the SEU theme. Working with the SEU missions and members of the OSS Support Network, the Forum will harness the assets of the SEU science community to: Inform, inspire, and involve the public in the explorations of the SEU science theme. Use the unique resources of the SEU science theme to enhance K-14 science, technology, and mathematics education. Identify and develop high-leverage opportunities for the SEU science community to contribute to education and outreach.

Rosendhal, Jeffrey↗