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NASA NTRSDate not supplied

BERT-based Topic Modeling and Information Retrieval to Support Fishbone Diagramming for Safe Integration of Unmanned Aircraft Systems in Wildfire Response

Recent concepts for emerging wildfire response operations have included unmanned aircraft systems (UAS) due to their increasing accessibility and capabilities. To integrate UAS into wildfire response safely, researchers have studied the use of large repositories of historic incident reports to improve the scope of root cause analysis. Recent work has emphasized applying state-of-the-art natural language processing techniques to extract useful information from these repositories. However, it has not yet been studied how these results can be interpreted and integrated into the systems engineering process. In this work, we propose a process in which Bidirectional Encoder Representations from Transformers (BERT)-based topic modeling and information retrieval are applied to a relevant set of documents in order to support the development of a fishbone diagram in a semiautomated process. High-level themes in the document set are identified using topic modeling, which are then refined and interpreted by a human analyst. Then, the themes are used to guide a finer search using information retrieval, which returns specific incident reports of relevance. This provides traceability to specific incidents as well as broader categorizations that comprise the fishbone branches. We apply the proposed process to relevant documents from NASA’s Aviation Safety Reporting System (ASRS). The proposed process is widely applicable when relevant documents are available, and the results from this study will be useful to identifying potential causes of wildfire response UAS incidents.

hazard analysis↗

NASA NTRSDate not supplied

BERT-based Topic Modeling and Information Retrieval to Support Fishbone Diagramming for Safe Integration of Unmanned Aircraft Systems in Wildfire Response

hazard analysis↗

NASA NTRS1980

Theory of positronium formation and positron emission at metal surfaces

The range of metallic surface processes available to the implanted positron is examined with a view to bare positron escape, positron surface state trapping, surface state detrapping, and positronium atom conversion. The stopping distance and its rms deviation are calculated. The effect of the elastic positron-ion core scattering, and the finite temperature corrections in the positron-phonon scattering are included. Overall conversion and emission efficiencies are calculated by solving an appropriate diffusion equation with boundary conditions set by the branching ratios for the surface processes. The temperature and incident energy dependence of the results for positronium atom conversion and positron emission efficiency are compared to experimental data.

Nieminen, R. M.↗

NASA NTRS2005

Process Developed for Generating Ceramic Interconnects With Low Sintering Temperatures for Solid Oxide Fuel Cells

Solid oxide fuel cells (SOFCs) have been considered as premium future power generation devices because they have demonstrated high energy-conversion efficiency, high power density, and extremely low pollution, and have the flexibility of using hydrocarbon fuel. The Solid-State Energy Conversion Alliance (SECA) initiative, supported by the U.S. Department of Energy and private industries, is leading the development and commercialization of SOFCs for low-cost stationary and automotive markets. The targeted power density for the initiative is rather low, so that the SECA SOFC can be operated at a relatively low temperature (approx. 700 C) and inexpensive metallic interconnects can be utilized in the SOFC stack. As only NASA can, the agency is investigating SOFCs for aerospace applications. Considerable high power density is required for the applications. As a result, the NASA SOFC will be operated at a high temperature (approx. 900 C) and ceramic interconnects will be employed. Lanthanum chromite-based materials have emerged as a leading candidate for the ceramic interconnects. The interconnects are expected to co-sinter with zirconia electrolyte to mitigate the interface electric resistance and to simplify the processing procedure. Lanthanum chromites made by the traditional method are sintered at 1500 C or above. They react with zirconia electrolytes (which typically sinter between 1300 and 1400 C) at the sintering temperature of lanthanum chromites. It has been envisioned that lanthanum chromites with lower sintering temperatures can be co-fired with zirconia electrolyte. Nonstoichiometric lanthanum chromites can be sintered at lower temperatures, but they are unstable and react with zirconia electrolyte during co-sintering. NASA Glenn Research Center s Ceramics Branch investigated a glycine nitrate process to generate fine powder of the lanthanum-chromite-based materials. By simultaneously doping calcium on the lanthanum site, and cobalt and aluminum on the chromium site, we could sinter the materials below 1400 C. The doping concentrations were adjusted so that the thermal expansion coefficient matched that of the zirconia electrolyte. Also, the investigation was focused on stoichiometric compositions so that the materials would have better stability. Co-sintering and chemical compatibility with zirconia electrolyte were examined by X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy (line scanning and dot map). The results showed that the materials bond well, but do not react, with zirconia electrolyte. The electric conductivity of the materials measured at 900 C in air was about 20 S/cm.

Zhong, Zhi-Min↗

DOE OSTI2022

Hydrological Perspectives on Integrated, Coordinated, Open, Networked (ICON) Science

Hydrologic sciences depend on data monitoring, analyses, and simulations of hydrologic processes to ensure safe, sufficient, and equal water distribution. These hydrologic data come from but are not limited to primary (lab, plot, and field experiments) and secondary sources (remote sensing, UAVs, hydrologic models) that typically follow FAIR Principles (Findable, Accessible, Interoperable, and Reusable: (go-fair.org)). Easy availability of FAIR data has become possible because the hydrology-oriented organizations have pushed the community to increase coordination of the protocols for generating data and sharing model platforms. In addition, networking at all levels has emerged with an invigorated effort to activate community science efforts that complement conventional data collection methods. However, it has become difficult to decipher various complex hydrologic processes with increasing data. Machine learning, a branch of artificial intelligence, provide more accurate and faster alternatives to better understand different hydrological processes. The Integrated, Coordinated, Open, Networked (ICON) framework provides a pathway for water users to include and respect diversity, equity, and inclusivity. In addition, ICONs support the integration of peoples with historically marginalized identities into this professional discipline of water sciences. This article comprises three independent commentaries about the state of ICON principles in hydrology and discusses the opportunities and challenges of adopting them.

(ICON) principles to address↗

NASA NTRS1984

Multispectral and geomorphic studies of processed Voyager 2 images of Europa

High resolution images of Europa taken by the Voyager 2 spacecraft were used to study a portion of Europa's dark lineations and the major white line feature Agenor Linea. Initial image processing of images 1195J2-001 (violet filter), 1198J2-001 (blue filter), 1201J2-001 (orange filter), and 1204J2-001 (ultraviolet filter) was performed at the U.S.G.S. Branch of Astrogeology in Flagstaff, Arizona. Processing was completed through the stages of image registration and color ratio image construction. Pixel printouts were used in a new technique of linear feature profiling to compensate for image misregistration through the mapping of features on the printouts. In all, 193 dark lineation segments were mapped and profiled. The more accurate multispectral data derived by this method was plotted using a new application of the ternary diagram, with orange, blue, and violet relative spectral reflectances serving as end members. Statistical techniques were then applied to the ternary diagram plots. The image products generated at LPI were used mainly to cross-check and verify the results of the ternary diagram analysis.

Meier, T. A.↗

DOE OSTI2023

Non-equilibrium low-temperature plasma-assisted combustion of iso-octane: Perturbing pyrolysis and oxidation kinetics

Here, in this study, a plasma-coupled flow reactor facility is used to examine the effects of non-equilibrium low-temperature plasmas on perturbing the pyrolysis and oxidation kinetics of iso-octane. Experiments were performed in highly dilute reactive mixtures of nitrogen, at near isothermal conditions for temperatures ranging from 523 K to 1203 K. Experiments cumulatively demonstrated enhanced chemical reactivity with the plasma for temperatures below 900 K, and a lowering of the hot-ignition temperature. Detailed kinetic insight was derived from a 0D plasma-coupled kinetic model, utilizing a constructed mechanism that combined both plasma-specific chemistry and the neutral combustion chemistry. For pyrolysis conditions, the model displayed relatively good agreement with fuel consumption and the formation of most intermediates compared to the experimental data, demonstrating the model is able to accurately predict primary radical formation from the plasma directly interacting with the fuel. Enhanced reactivity was attributed to collisional quenching of excited-states of N 2 with fuel, which led to efficient fuel fragmentation and enhancement of the H-radical flux. For oxidation conditions, the model displayed satisfactory agreement with the experiments. Model predictions were able to accurately predict fuel consumption and most intermediate speciation data for T > 800 K, but most discrepancies were towards T < 800 K in particular with oxygenated intermediates. In the presence of oxygen, plasma effects were predominantly spent on efficient enhancement of O- and H-radical fluxes, leading to further fuel fragmentation and initiation of both the OH- and HO 2 -radical pools. Subsequent reactivity of iso-octane was then dictated by the response of the temperature-dependent neutral chemistry. At low-temperatures (T = 643 K), enhanced fuel radicals and O 2 -additon chemistry lead to the formation of oxygenated species, while at intermediate temperatures (T = 843 K) net decrease in OH-radical reactivity led to an increase in hydrocarbon speciation. Near the self-ignition threshold (T = 1163 K), radicals generated by high-temperature branching reactions dominate the oxidation process and effectively ignition. This study ultimately demonstrated that the enhancement of radicals afforded by the plasma causes a deviation in known understanding of iso-octane kinetics in some regards and warrants future studies to reconcile these discrepancies.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2022

Microscopic Dynamics of Inverse Wormlike Micelles Probed Using X-ray Photon Correlation Spectroscopy

Wormlike micelles (WLMs) are ubiquitous viscoelastic modifiers that share properties with polymer solutions. While 5 their macroscopic rheology is well-understood, their microscopic dynamics are less studied because they span a large range of time 6 and length scales. In this work, we demonstrate the use of X-ray photon correlation spectroscopy to interrogate the segmental 7 dynamics of inverse WLM solutions swollen with a rubidium chloride solution. We observe a diffusive scaling of the dynamics and 8 extract a temperature-dependent diffusion coefficient, which we associate with the thermal interactions of the slow segmental 9 dynamics near entanglement points. Further, we probe this relaxation process across the unbranched to branched topological transition and 10 find no microstructural evidence of branch formation in the slow mode. Instead, we observe that the dynamics become more 11 homogeneous and prominent as the temperature is reduced and water content increases.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2020

Solvent oligomerization pathways facilitated by electrolyte additives during solid-electrolyte interphase formation

The solid–electrolyte interphase (SEI) layer formation is known to play an important role in determining the lifetime of lithium-ion batteries. A thin, stable SEI layer is linked to overall improved battery performance and longevity, however, the factors and mechanisms that lead to optimal SEI morphology and composition are not well understood. Inclusion of electrolyte additives (fluoroethylene carbonate, FEC; and vinylene carbonate, VC) is often necessary for improving SEI characteristics. To understand how these electrolyte additives impact SEI formation, we employed molecular dynamics (MD) and density functional theory (DFT) simulations to study the reaction networks and oligomerization pathways, respectively, for three systems containing ethylene carbonate (EC), a lithium ion, and FEC or VC. MD simulations suggest radical oligomerization pathways analogous to traditional oligomerization with nucleophilic alkoxide species via SN1 reaction mechanisms. Both S N 1 and S N 2 mechanisms were studied for all three systems using DFT. Oligomerization reactions were studied with both a standard alkoxide species and a ring-opened EC radical as the nucleophiles and EC, FEC, and VC as the electrophiles. For all cases, FEC and VC exhibited lower free energy barriers and more stable adducts when compared with EC. We conclude that one of the role of additives is to modify the oligomerization process of EC by introducing branching points (FEC) or termination points (VC).

25 ENERGY STORAGE↗

DOE OSTI2025

Identifying impacts of contact tracing on HIV epidemiological inference from phylogenetic data

Abstract Robust sampling methods are foundational to inferences using phylogenies. Yet the impact of using contact tracing, a type of non-uniform sampling used in public health applications such as infectious disease outbreak investigations, has not been investigated in the molecular epidemiology field. To understand how contact tracing influences a recovered phylogeny, we developed a new simulation tool called SEEPS (Sequence Evolution and Epidemiological Process Simulator) that allows for the simulation of contact tracing and the resulting transmission tree, pathogen phylogeny, and corresponding virus genetic sequences. Importantly, SEEPS takes within-host evolution into account when generating pathogen phylogenies and sequences from transmission histories. Using SEEPS, we demonstrate that contact tracing can significantly impact the structure of the resulting tree, as described by popular tree statistics. Contact tracing generates phylogenies that are less balanced than the underlying transmission process, less representative of the larger epidemiological process, and affects the internal/external branch length ratios that characterize specific epidemiological scenarios. We also examined real data from a 2007–2008 Swedish HIV-1 outbreak and the broader 1998–2010 European HIV-1 epidemic to highlight the differences in contact tracing and expected phylogenies. Aided by SEEPS, we show that the data collection of the Swedish outbreak was strongly influenced by contact tracing even after downsampling, while the broader European Union epidemic showed little evidence of universal contact tracing, agreeing with the known epidemiological information about sampling and spread. Overall, our results highlight the importance of including possible non-uniform sampling schemes when examining phylogenetic trees. For that, SEEPS serves as a useful tool to evaluate such impacts, thereby facilitating better phylogenetic inferences of the characteristics of a disease outbreak. SEEPS is available at https://github.com/MolEvolEpid/SEEPS.

Virology↗

DOE OSTI2022

Exploring the S-process History in the Galactic Disk: Cerium Abundances and Gradients in Open Clusters from the OCCAM/APOGEE Sample

The APOGEE Open Cluster Chemical Abundances and Mapping survey is used to probe the chemical evolution of the s-process element cerium in the Galactic disk. Cerium abundances were derived from measurements of Ce ii lines in the APOGEE spectra using the Brussels Automatic Code for Characterizing High Accuracy Spectra in 218 stars belonging to 42 open clusters. Our results indicate that, in general, for ages < 4 Gyr, younger open clusters have higher [Ce/Fe] and [Ce/α-element] ratios than older clusters. In addition, metallicity segregates open clusters in the [Ce/X]–age plane (where X can be H, Fe, or the α-elements O, Mg, Si, or Ca). These metallicity-dependent relations result in [Ce/Fe] and [Ce/α] ratios with ages that are not universal clocks. Radial gradients of [Ce/H] and [Ce/Fe] ratios in open clusters, binned by age, were derived for the first time, with d[Ce/H]/dR GC being negative, while d[Ce/Fe]/dR GC is positive. [Ce/H] and [Ce/Fe] gradients are approximately constant over time, with the [Ce/Fe] gradient becoming slightly steeper, changing by ~+0.009 dex kpc -1 Gyr -1 . Both the [Ce/H] and [Ce/Fe] gradients are shifted to lower values of [Ce/H] and [Ce/Fe] for older open clusters. The chemical pattern of Ce in open clusters across the Galactic disk is discussed within the context of s-process yields from asymptotic giant branch (AGB) stars, gigayear time delays in Ce enrichment of the interstellar medium, and the strong dependence of Ce nucleosynthesis on the metallicity of its AGB stellar sources.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS1983

Eddy current X-Y scanner system

The Nondestructive Evaluation Branch of the Materials and Processes Laboratory became aware of a need for a miniature, portable X-Y scanner capable of performing eddy current or other nondestructive testing scanning operations such as ultrasonic, or small areas of flat plate. The technical description and operational theory of the X-Y scanner system designed and built to fulfill this need are covered. The scanner was given limited testing and performs according to its design intent, which is to scan flat plate areas of approximately 412 sq cm (64 sq in) during each complete cycle of scanning.

Kurtz, G. W.↗

NASA NTRS2000

A Dream of a Mission: Stellar Imager and Seismic Probe

The Stellar Imager and Seismic Probe (SISP) is a mission to understand the various effects of magnetic fields of stars, the dynamos that generate them, and the internal structure and dynamics of the stars in which they exist. The ultimate goal is to achieve the best-possible forecasting of solar activity on times scales ranging up to decades, and an understanding of the impact of stellar magnetic activity on astrobiology and life in the Universe. The road to that goal will revolutionize our understanding of stars and stellar systems, the building blocks of the Universe. SISP will zoom in on what today - with few exceptions - we only know as point sources, revealing processes never before seen, thus providing a tool to astrophysics as fundamental as the microscope is to the study of life on Earth. SISP is an ultraviolet aperture-synthesis imager with 8-10 telescopes with meter-class apertures, and a central hub with focal-plane instrumentation that allows spectrophotometry in passbands as narrow as a few Angstroms up to hundreds of Angstroms. SISP will image stars and binaries with one hundred to one thousand resolution elements on their surface, and sound their interiors through asteroseismology to image internal structure, differential rotation, and large-scale circulations; this will provide accurate knowledge of stellar structure and evolution and complex transport processes, and will impact numerous branches of (astro)physics ranging from the Big Bang to the future of the Universe. Fitting naturally within the NASA long-term time line, SISP complements defined missions, and with them will show us entire other solar systems, from the central star to their orbiting planets.

Carpenter, Kenneth G.↗

NASA NTRS1996

Telemetry Systems

Goddard Space Flight Center developed satellite telemetry processing technology to meet NASA's sophisticated processing requirements. The Microelectronic Systems Branch, a 'company' within Goddard, provided NASA with the telemetry data systems from 1985 to 1994. TSI/Telsys, Inc. was then founded to commercialize the systems and began operations on October 1, 1995. The system aids the remote sensing industry by providing affordable and quick access to data collected from space.

Source record↗

NASA NTRS2000

Laboratory investigation of the contribution of complex aromatic/aliphatic polycyclic hybrid molecular structures to interstellar ultraviolet extinction and infrared emission

We have demonstrated by experiment that, in an energetic environment, a simple polycyclic aromatic hydrocarbon (PAH) such as naphthalene will undergo chemical reactions that produce a wide array of more complex species (an aggregate). For a stellar wind of a highly evolved star (post-asymptotic giant branch [post-AGB]), this process would be in addition to what is expected from reactions occurring under thermodynamic equilibrium. A surprising result of that work was that produced in substantial abundance are hydrogenated forms that are hybrids of polycyclic aromatic and polycyclic alkanes. Infrared spectroscopy described here reveals a spectral character for these materials that has much in common with that observed for the constituents of circumstellar clouds of post-AGB stars. It can be demonstrated that a methylene (-CH2-) substructure, as in cycloalkanes, is the likely carrier of the 6.9 microns band emission of dust that has recently been formed around IRAS 22272+5433, NGC 7027, and CPD -56 8032. Ultraviolet spectroscopy previously done with a lower limit of 190 nm had revealed that this molecular aggregate can contribute to the interstellar extinction feature at 2175 angstroms. We have now extended our UV spectroscopy of these materials to 110 nm by a vacuum ultraviolet technique. That work, described here, reveals new spectral characteristics and describes how material newly formed during the late stages of stellar evolution could have produced an extinction feature claimed to exist at 1700 angstroms in the spectrum of HD 145502 and also how the newly formed hydrocarbon material would be transformed/aged in the general interstellar environment. The contribution of this molecular aggregate to the rise in interstellar extinction at wavelengths below 1500 angstroms is also examined. The panspectral measurements of the materials produced in the laboratory, using plasmas of H, He, N, and O to convert the simple PAH naphthalene to an aggregate of complex species, provide insight into possible molecular structure details of newly formed hydrocarbon-rich interstellar dust and its transformation into aged material that becomes resident in the interstellar medium. Specifically the presence of naphthalene-like and butadiene-like conjugated structures as chromophores for the 2175 angstroms ultraviolet extinction feature is indicated.

NASA Discipline Exobiology↗

DOE OSTI2025

Stable single-site organonickel catalyst preferentially hydrogenolyses branched polyolefin C–C bonds

Current methods of processing accumulated polyolefin waste typically require harsh conditions, precious metals or high metal loadings to achieve appreciable activities. Here, in this work, we examined supported, single-site organonickel catalysts for polyolefin upcycling. Chemisorption of Ni(COD) 2 (COD, 1,5-cyclooctadiene) onto Brønsted acidic sulfated alumina (AlS) yields a highly electrophilic Ni(I) precatalyst, AlS/Ni(COD) 2 , which is converted under H 2 to the active AlS/Ni II H catalyst. This single-site system exhibits unique hydrogenolysis selectivity that favours cleaving branched polyolefin C–C linkages, enabling the hydrogenolytic separation of polyethylene and isotactic polypropylene (iPP) mixtures. Moreover, AlS/Ni II H remains highly selective and active for hydrogenolysis of iPP admixed with polyvinyl chloride, and the spent catalyst can be repeatedly regenerated by AlEt3 treatment. Experimental mechanistic analysis and density functional theory modelling reveal a turnover-limiting C–C scission pathway featuring β-alkyl transfer and strong olefin binding. These results highlight the potential of nickel-based systems for the selective upcycling of complex plastic waste streams.

green chemistry↗

NASA NTRS1976

Machine processing of remotely acquired data

The two major branches of remote sensing are based on image orientation and numerical orientation. Numerically oriented systems tend to involve computers for data analysis. In designing an information-gathering system, the sensor as well as the means of analysis must be well mated to the type of system orientation. Attention is given to sensor types as related to system types, the multispectral approach and pattern recognition, the multispectral scanner as data source, an illustrative example, procedural details in the use of pattern recognition, the speed and cost of data processing, the use of spatial information, and data preprocessing steps.

Landgrebe, D. A.↗

NASA NTRS2010

Designing and Implementing an OVERFLOW Reader for ParaView and Comparing Performance Between Central Processing Units and Graphical Processing Units

In the Applied Aerosciences and CFD branch at Johnson Space Center, computational simulations are run that face many challenges. Two of which are the ability to customize software for specialized needs and the need to run simulations as fast as possible. There are many different tools that are used for running these simulations and each one has its own pros and cons. Once these simulations are run, there needs to be software capable of visualizing the results in an appealing manner. Some of this software is called open source, meaning that anyone can edit the source code to make modifications and distribute it to all other users in a future release. This is very useful, especially in this branch where many different tools are being used. File readers can be written to load any file format into a program, to ease the bridging from one tool to another. Programming such a reader requires knowledge of the file format that is being read as well as the equations necessary to obtain the derived values after loading. When running these CFD simulations, extremely large files are being loaded and having values being calculated. These simulations usually take a few hours to complete, even on the fastest machines. Graphics processing units (GPUs) are usually used to load the graphics for computers; however, in recent years, GPUs are being used for more generic applications because of the speed of these processors. Applications run on GPUs have been known to run up to forty times faster than they would on normal central processing units (CPUs). If these CFD programs are extended to run on GPUs, the amount of time they would require to complete would be much less. This would allow more simulations to be run in the same amount of time and possibly perform more complex computations.

Chawner, David M.↗