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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Analysis of stress-rupture data from S-glass composites.

Both composite and free strands have been tested to study matrix effectiveness. Glass from different lots were used, and processing parameters were varied to demonstrate the effects of material variability. The statistical patterns that emerge from these experiments show that lifetime distributions are characteristically skewed. As a class, the lifetime distributions are well approximated by the reduced form of the Weibull distribution. The strength retention data display little early degradation. The retained-strength distributions can also be classed as Weibull distributions. A statistical model applied to the data gives predictions of progressive failure, strength retention path, and expected life for two basic types of internal fracture processes.

Robinson, E. Y.↗
NASA NTRS1973

Antiphase domains in lunar plagioclase

The paper is a compilation of data on antiphase domains in lunar plagioclase. New observations and reports in the literature are tabulated and discussed. In the pattern which emerges (but is still very incomplete), it appears that b-domains, which except for the An 82 bytownite from the Stillwater complex have only been observed in lunar feldspars, occur in the anorthite range An 80 to 95. Especially in the sodium rich part there seems to be a close relation between an exsolution structure and b-APB's. The c-APB's are found in anorthites An 95 to 100 and for a given An-content they are larger for metamorphic than for volcanic anorthites. Near An 95, c- and b-domains can be observed in the same crystal. The c-domains disappear when heated above 1200 C; they are not affected by heating below 600 C. This implies that calcic anorthite without c-domains must have been rapidly quenched from high temperatures.

Wenk, H.-R.↗
NASA NTRS1977

On the nature of photospheric magnetic fields beneath large coronal holes

Proposed mechanisms for the formation of coronal holes are considered; the crucial issue appears to be whether the holes are permeated by rigidly rotating fields. It is suggested that the interaction between such a field and the differentially rotating, diffusive solar envelope will produce a fore aft asymmetry in the distribution of fields which emerge to the photosphere. An initial study is carried out in the context of an illustrative example, and the results indicate that the asymmetry may be observed for a certain range of parameters involving the properties of the solar envelope and the characteristic size of the emerging field pattern.

Frankenthal, S.↗
NASA NTRS1980

Steady flows in the chromosphere and transition-zone above active regions as observed by OSO-8

Two years of data from the University of Colorado ultraviolet spectrometer aboard OSO-8 were searched for steady line-of-sight flows in the chromosphere and transition-zone above active regions. The most conspicuous pattern that emerges from this data set is that many sunspots show persistent blueshifts of transition-zone lines indicating velocities of about 20 km/s with respect to the surrounding plage areas. The data show much smaller shifts in ultraviolet emission lines arising from the chromosphere: the shifts are frequently to the blue, but sometimes redshifts do occur. Plage areas often show a redshift of the transition-zone lines relative to the surrounding quiet areas, and a strong gradient of the vertical component of the velocity is evident in many plages. One area of persistent blueshift was observed in the transition-zone above an active region filament. The energy requirement of these steady flows over sunspots is discussed.

Lites, B. W.↗
NASA NTRS1990

Current plate motions

A global plate motion model, named NUVEL-1, which describes current plate motions between 12 rigid plates is described, with special attention given to the method, data, and assumptions used. Tectonic implications of the patterns that emerged from the results are discussed. It is shown that wide plate boundary zones can form not only within the continental lithosphere but also within the oceanic lithosphere; e.g., between the Indian and Australian plates and between the North American and South American plates. Results of the model also suggest small but significant diffuse deformation of the oceanic lithosphere, which may be confined to small awkwardly shaped salients of major plates.

Demets, C.↗
NASA NTRS1992

The distribution of anorthosite on the nearside of the moon

Remote sensing studies of lunar basin and crater deposits were conducted in order to determine the composition of surface units and to investigate the stratigraphy of the lunar crust. These studies have combined both visible and near-IR spectral observations with multispectral imaging in order to determine the lithology of relatively small portions (2-10 km) of the lunar surface. Numerous deposits of pure anorthosite (plagioclase greater than 90 percent) were identified and an interesting pattern has emerged. The purposes of this report are as follows: (1) to summarize the results of our previous studies of the distribution of anorthosite; (2)to present new findings concerning the modes of occurrence of lunar anorthosite; and (3) to assess the implication for the magma ocean hypothesis.

Hawke, B. R.↗
NASA NTRS1993

Mapping of the Ronda peridotite massif (Spain) from AVIRIS spectro-imaging survey: A first attempt

In both AVIRIS and ISM data, through the use of mixing models, geological boundaries of the Ronda massif are identified with respect to the surrounding rocks. We can also yield first-order vegetation maps. ISM and AVIRIS instruments give consistent results. On the basis of endmember fraction images, it is then possible to discard areas highly vegetated or not belonging to the peridotite massif. Within the remaining part of the mosaic, spectro-mixing analysis reveals spectral variations in the peridotite massif between the well-exposed areas. Spatially organized units are depicted, related to differences in the relative depth of the absorption band at 1 micron, and it may be due to a different pyroxene content. At this stage, it is worth noting that, although mineralogical variations observed in the rocks are at a sub-pixel scale for the airborne analysis, we see an emerging spatial pattern in the distribution of spectral variations across the massif which might be prevailingly related to mineralogy. Although it is known from fieldwork that the Ronda peridotite massif exhibits mineralogical variations at local scale in the content of pyroxene, and at regional scale in different mineral facies, ranging from garnet-, to spinel- to plagioclase-lherzolites, no attempt has been done yet to produce a synoptic map relating the two scales of analysis. The present work is a first attempt to reach this objective, though a lot more work is still required. In particular, for the purpose of mineralogical interpretation, it is critical to relate the airborne observation to field work and laboratory spectra of Ronda rocks already obtained, with the use of image endmembers and associated reference endmembers. Also, the pretty rough linear mixing model used here is taken as a 'black-box' process which does not necessarily apply correctly to the physical situation at the sub-pixel level. One may think of using the ground-truth observations bearing on the sub-pixel statistical characteristics (texture, structural pattern, surface distribution and vegetation contribution (grass,..)) to produce a more advanced mixing model, physically appropriate to the geologic and environmental contexts.

Pinet, P. C.↗
NASA NTRS2012

Planetary Lake Lander - A Robotic Sentinel to Monitor a Remote Lake

The Planetary Lake Lander Project is studying the impact of rapid deglaciation at a high altitude alpine lake in the Andes, where disrupted environmental, physical, chemical, and biological cycles result in newly emerging natural patterns. The solar powered Lake Lander robot is designed to monitor the lake system and characterize both baseline characteristics and impacts of disturbance events such as storms and landslides. Lake Lander must use an onboard adaptive science-on-the-fly approach to return relevant data about these events to mission control without exceeding limited energy and bandwidth resources. Lake Lander carries weather sensors, cameras and a sonde that is winched up and down the water column to monitor temperature, dissolved oxygen, turbidity and other water quality parameters. Data from Lake Lander is returned via satellite and distributed to an international team of scientists via web-based ground data systems. Here, we describe the Lake Lander Project scientific goals, hardware design, ground data systems, and preliminary data from 2011. The adaptive science-on-the-fly system will be described in future papers.

Pedersen, Liam↗
NASA NTRS2015

Cyber-Attack Methods, Why They Work on Us, and What to Do

Basic cyber-attack methods are well documented, and even automated with user-friendly GUIs (Graphical User Interfaces). Entire suites of attack tools are legal, conveniently packaged, and freely downloadable to anyone; more polished versions are sold with vendor support. Our team ran some of these against a selected set of projects within our organization to understand what the attacks do so that we can design and validate defenses against them. Some existing defenses were effective against the attacks, some less so. On average, every machine had twelve easily identifiable vulnerabilities, two of them "critical". Roughly 5% of passwords in use were easily crack-able. We identified a clear set of recommendations for each project, and some common patterns that emerged among them all.

cybersecurity↗
NASA NTRS2021

Eastern Equatorial Pacific Warming Delayed By Aerosols and Thermostat Response to Co2 Increase

Understanding the tropical Pacific response to global warming remains challenging. Here, we use a range of CMIP6 greenhouse warming experiments to assess the recent and future evolution of the equatorial Pacific east-west temperature gradient and corresponding Walker circulation. In abrupt CO2-increase scenarios many models generate an initial strengthening of this gradient resembling an ocean thermostat (OT), followed by a small weakening; other models generate an immediate weakening that becomes progressively stronger establishing a pronounced eastern equatorial Pacific (EP) warming pattern. The initial response in these experiments is a strong predictor for the future EP pattern simulated in both abrupt and realistic warming scenarios, but not in historical simulations showing no multi-model trend. The likely explanation is that the recent CO2-driven changes in the tropical Pacific are masked by aerosol effects and a potential OT-related delay, while the EP warming pattern will emerge as greenhouse gases overcome aerosol forcing.

Climate and Earth system modelling↗
DOE OSTI2025

An MLCommons Scientific Benchmarks Ontology

Scientific machine learning research spans diverse domains and data modalities, yet existing benchmark efforts remain siloed and lack standardization. This makes novel and transformative applications of machine learning to critical scientific use-cases more fragmented and less clear in pathways to impact. This paper introduces an ontology for scientific benchmarking developed through a unified, community-driven effort that extends the MLCommons ecosystem to cover physics, chemistry, materials science, biology, climate science, and more. Building on prior initiatives such as XAI-BENCH, FastML Science Benchmarks, PDEBench, and the SciMLBench framework, our effort consolidates a large set of disparate benchmarks and frameworks into a single taxonomy of scientific, application, and system-level benchmarks. New benchmarks can be added through an open submission workflow coordinated by the MLCommons Science Working Group and evaluated against a six-category rating rubric that promotes and identifies high-quality benchmarks, enabling stakeholders to select benchmarks that meet their specific needs. The architecture is extensible, supporting future scientific and AI/ML motifs, and we discuss methods for identifying emerging computing patterns for unique scientific workloads. The MLCommons Science Benchmarks Ontology provides a standardized, scalable foundation for reproducible, cross-domain benchmarking in scientific machine learning. A companion webpage for this work has also been developed as the effort evolves: https://mlcommons-science.github.io/benchmark/

Hawks, Ben [Fermilab] (ORCID:0000000157000288)↗
DOE OSTI2012

Phase emerging from intramonolayer cycloaddition on micro-patterned monolayer

Cu(I)-catalyzed cycloaddition between azide and acetylene, followed by hydrolysis of ester were performed on micro-patterned self-assembled monolayer to produce smaller features. The reactions were initially performed on mixed monolayers and analysed by water contact angle (CA) and confirmed by X-ray Photoelectron Spectroscopy (XPS). The contact angle measurement has shown a drastic wetting of water on the surface of mixed monolayer indicating that the terminal groups on mixed monolayer has changed into carboxylic acid and hydroxyl terminals. The reactions work in a similar way on micro-patterned SAM and analyzed by using friction force microscope. The emerging of the new lines with high friction force on the border suggested a successful intramonolayer reactions on the border of the patterned SAM.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Oblique shock breakout in supernovae and gamma-ray bursts. II. Numerical solutions for non-relativistic pattern speeds

Non-spherical explosions develop non-radial flows as the pattern of shock emergence progresses across the stellar surface. In supernovae, these flows can limit ejecta speeds, stifle shock breakout emission, and cause collisions outside the star. Similar phenomena occur in stellar and planetary collisions, tidal disruption events, accretion-induced collapses, and propagating detonations. We present two-dimensional, nested-grid Athena simulations of non-radial shock emergence in a frame comoving with the breakout pattern, focusing on the adiabatic, non-relativistic limit in a plane stratified envelope. We set boundary conditions using a known self-similar solution and explore the role of box size and resolution on the result. The shock front curves toward the stellar surface, and exhibits a kink from which weak discontinuities originate. Flow around the point of shock emergence is neither perfectly steady nor self-similar. Waves and vortices, which are not predominantly due to grid effects, emanate from this region. The post-shock flow is deflected along the stellar surface and its pressure disturbs the stellar atmosphere upstream of the emerging shock. We use the numerical results and their analytical limits to predict the effects of radiation transfer and gravity, which are not included in our simulations.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1998

A natural view of microbial biodiversity within hot spring cyanobacterial mat communities

This review summarizes a decade of research in which we have used molecular methods, in conjunction with more traditional approaches, to study hot spring cyanobacterial mats as models for understanding principles of microbial community ecology. Molecular methods reveal that the composition of these communities is grossly oversimplified by microscopic and cultivation methods. For example, none of 31 unique 16S rRNA sequences detected in the Octopus Spring mat, Yellowstone National Park, matches that of any prokaryote previously cultivated from geothermal systems; 11 are contributed by genetically diverse cyanobacteria, even though a single cyanobacterial species was suspected based on morphologic and culture analysis. By studying the basis for the incongruity between culture and molecular samplings of community composition, we are beginning to cultivate isolates whose 16S rRNA sequences are readily detected. By placing the genetic diversity detected in context with the well-defined natural environmental gradients typical of hot spring mat systems, the relationship between gene and species diversity is clarified and ecological patterns of species occurrence emerge. By combining these ecological patterns with the evolutionary patterns inherently revealed by phylogenetic analysis of gene sequence data, we find that it may be possible to understand microbial biodiversity within these systems by using principles similar to those developed by evolutionary ecologists to understand biodiversity of larger species. We hope that such an approach guides microbial ecologists to a more realistic and predictive understanding of microbial species occurrence and responsiveness in both natural and disturbed habitats.

Review↗
DOE OSTI2014

Routes to spatiotemporal chaos in Kerr optical frequency combs

We investigate the various routes to spatiotemporal chaos in Kerr optical frequency combs, obtained through pumping an ultra-high Q-factor whispering-gallery mode resonator with a continuous-wave laser. The Lugiato–Lefever model is used to build bifurcation diagrams with regards to the parameters that are externally controllable, namely, the frequency and the power of the pumping laser. We show that the spatiotemporal chaos emerging from Turing patterns and solitons display distinctive dynamical features. Experimental spectra of chaotic Kerr combs are also presented for both cases, in excellent agreement with theoretical spectra.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2026

Emergence of complex-regular eutectic patterns in Al–Ge: Observations from correlative nano-imaging

Eutectic solidification exemplifies nonequilibrium pattern formation, making it a well-studied moving boundary problem. Yet the mechanisms behind the formation of complex-regular microstructures – particularly in highly anisotropic systems with a significant volume fraction of a faceted phase – remain poorly understood. Our understanding of such systems is made complicated by the nonlinear interface kinetics and unique growth dynamics characteristic of faceted phases. To address these challenges, we investigate a model Al–Ge eutectic system, where the faceted Ge phase constitutes a substantial volume fraction (~0.35) and where the two solid phases arrange into so-called “fishbone” or “feather” complex-regular patterns. Using synchrotron-based x-ray nano-imaging and nanotomography with high spatial resolution (22 nm per pixel), we capture in real-time the evolution of the solid–liquid interfaces and the resulting three-dimensional microstructures in this faceted/non-faceted eutectic system. By integrating these observations with electron backscattered diffraction, we elucidate the crystallographic biases on the solidification process and the mechanisms driving the formation of such complex-regular microstructures. These findings inform a new growth model for irregular eutectics in (near-)symmetrical phase diagrams, offering insight on advanced microstructural design and processing strategies. More broadly, we demonstrate how interfacial curvature is generated in irregular eutectic alloys and how it depends on the volume fraction of the faceted phase.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Using a Genetic Algorithm to Optimize Configurations in a Data-Driven Application

Users of highly-configurable software systems often want to optimize a particular objective such as improving a functional outcome or increasing system performance. One approach is to use an evolutionary algorithm. However, many applications today are data-driven, meaning they depend on inputs or data which can be complex and varied. Hence, a search needs to be run (and re-run) for all inputs, making optimization a heavy-weight and potentially impractical process. In this paper, we explore this issue on a data-driven highly-configurable scientific application. We build an exhaustive database containing 3,000 configurations and 10,000 inputs, leading to almost 100 million records as our oracle, and then run a genetic algorithm individually on each of the 10,000 inputs. We ask if (1) a genetic algorithm can find configurations to improve functional objectives; (2) whether patterns of best configurations over all input data emerge; and (3) if we can we use sampling to approximate the results. We find that the original (default) configuration is best only 34% of the time, while clear patterns emerge of other best configurations. Out of 3,000 possible configurations, only 112 distinct configurations achieve the optimal result at least once across all 10,000 inputs, suggesting the potential for lighter weight optimization approaches. We show that sampling of the input data finds similar patterns at a lower cost.

Sinha, Urjoshi↗
DOE OSTI2023

Generating Mixed Patterns of Residential Segregation: An Evolutionary Approach

The Schelling model of residential segregation has demonstrated that even the slightest preference for neighbors of the same race can be amplified into community-wide segregation. However, these models are unable to simulate mixed, coexisting patterns of segregation and integration, which have been seen to exist in cities. Using evolutionary model discovery we demonstrate how including social factors beyond racial bias when modeling relocation behavior enables the emergence of strongly mixed patterns. Our results indicate that the emergence of mixed patterns is better explained by multiple factors influencing the decision to relocate; the most important being the interaction of nonlinear, rapidly diminishing racial bias with a recent, historical tendency to move. Additionally, preference for less isolated neighborhoods or preference for neighborhoods with longer residing neighbors may produce weaker mixed patterns. Finally, this work highlights the importance of exploring the influence of multiple hypothesized factors of decision making, and their interactions, within agent rules, when studying emergent outcomes generated by agent-based models of complex social systems.

97 MATHEMATICS AND COMPUTING↗