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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 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Updates to the Spatial Analysis and Decision Assistance (SADA) Freeware Tool - 16583

SADA is a collaboration between the University of Tennessee and Oak Ridge National Laboratory to present a freeware desktop application integrating environmental risk analytics, spatial modeling, and decision sciences for use at EPA, NRC, DOE, and DoD contaminated sites. The software embeds risk assessment, uncertainty modeling, and downstream decision processes within a spatial context. Updates to Version 6 will provide will include a rich GIS environment and a new 3-D visualization model which permits immersive visualization of contamination, with topology, and the built environment. The risk models presented are developed in conjunction with Superfund to implement all scenarios in their Regional Screening Levels (RSLs) and radionuclide preliminary remediation goals (PRGs). In addition, SADA will be able to ingest high resolution LandScan population data providing insights into the proximity of population to contamination. A brief overview of the progress in provided along with anticipated next steps. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS2003

Development of vestibular afferent projections into the hindbrain and their central targets

In contrast to most other sensory systems, hardly anything is known about the neuroanatomical development of central projections of primary vestibular neurons and how their second order target neurons develop. Recent data suggest that afferent projections may develop not unlike other sensory systems, forming first the overall projection by molecular means followed by an as yet unspecified phase of activity mediated refinement. The latter aspect has not been tested critically and most molecules that guide the initial projection are unknown.The molecular and topological origin of the vestibular and cochlear nucleus neurons is also only partially understood. Auditory and vestibular nuclei form from several rhombomeres and a given rhombomere can contribute to two or more auditory or vestibular nuclei. Rhombomere compartments develop as functional subdivisions from a single column that extends from the hindbrain to the spinal cord. Suggestions are provided for the molecular origin of these columns but data on specific mutants testing these proposals are not yet available. Overall, the functional significance of both overlapping and segregated projections are not yet fully experimentally explored in mammals. Such lack of details of the adult organization compromises future developmental analysis.

Review↗
DOE OSTI2019

Analysis of Hybrid Smart Grid Communication Network Designs for Distributed Energy Resources Coordination

The rapid growth of distributed energy resources (DERs) has prompted increasing interest in the monitoring and control of DERs through hybrid smart grid communications. This paper develops a new method to investigate the impact of DER penetrations and applications on hybrid communications network designs. A suite of hybrid communications simulation models are developed using Network Simulator 3 (ns-3). The smart grid communications topologies with different DER penetrations are built on the utility-scale distribution grid. The simulation results show that (i) with increasing photovoltaic penetrations, nine hybrid communications designs achieve the expected latency albeit with higher packet loss rate; and (ii) both BPLC-Ethernet and BPLC-WiMAX designs can accommodate the DER applications with a high data rate up to 100 Mbps.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2012

Sr{sub 7}Ge{sub 6}, Ba{sub 7}Ge{sub 6} and Ba{sub 3}Sn{sub 2} -Three new binary compounds containing dumbbells and four-membered chains of tetrel atoms with considerable Ge-Ge {pi}-bonding character

The germanides Sr{sub 7}Ge{sub 6} and Ba{sub 7}Ge{sub 6} as well as the stannide Ba{sub 3}Sn{sub 2} were prepared by arc melting and annealing in welded tantalum ampoules using induction as well as resistance furnaces. The compounds were investigated by powder and single crystal X-ray diffraction. Sr{sub 7}Ge{sub 6} and Ba{sub 7}Ge{sub 6} crystallize in the Ca{sub 7}Sn{sub 6} structure type (space group Pmna, Z=4: a=7.777(2) A, b=23.595(4) A, c=8.563(2) A, wR{sub 2}=0.081 (all data), 2175 independent reflections, 64 variable parameters for Sr{sub 7}Ge{sub 6} and a=8.0853(6) A, b=24.545(2) A, c=8.9782(8) A, wR{sub 2}=0.085 (all data), 2307 independent reflections, 64 variable parameters for Ba{sub 7}Ge{sub 6}). Ba{sub 3}Sn{sub 2} crystallizes in an own structure type with the space group P4{sub 3}2{sub 1}2, Z=4, a=6.6854(2) A, c=17.842(2) A, wR{sub 2}=0.037 (all data), 1163 independent reflections, 25 variable parameters. In Sr{sub 7}Ge{sub 6} and Ba{sub 7}Ge{sub 6} the Ge atoms are arranged as Ge{sub 2} dumbbells and Ge{sub 4} four-membered atom chains. Their crystal structures cannot be rationalized according to the (8-N) rule. In contrast, Ba{sub 3}Sn{sub 2} presents Sn{sub 2} dumbbells as a main structural motif and thereby can be described as an electron precise Zintl phase. The chemical bonding situation in these structures is discussed on the basis of partial and total Density Of States (DOS) curves, band structures including fatbands, topological analysis of the Electron Localization Function (ELF) as well as Bader analysis of the bond critical points using the programs TB-LMTO-ASA and WIEN2K. While Ba{sub 3}Sn{sub 2} reveals semiconducting behaviour, all germanides Ae{sub 7}Ge{sub 6} (Ae=Ca, Sr, and Ba) show metallic properties and a considerable {pi}-bonding character between the Ge atoms of the four-membered chains and the dumbbells. The {pi}-bonding character of the germanides is best reflected by the resonance hybrid structures {l_brace}[Ge-Ge]{sup 6-}/[Ge-{sup ....}Ge-{sup ....}Ge-{sup ....}Ge]{sup 8-}{r_brace}{r_reversible}{l_brace}[Ge=Ge]{sup 4-}/[Ge-Ge-Ge-Ge]{sup 10-}{r_brace}. - Graphical abstract: The structure of Ba{sub 3}Sn{sub 2} contains Sn{sub 2} dumbbells as a main structural motif and thereby can be described as an electron precise Zintl phase. Ge{sub 2} dumbbells and Ge{sub 4} four-membered atom chains are the predominant features in Sr{sub 7}Ge{sub 6} and Ba{sub 7}Ge{sub 6}. Their crystal structures cannot be rationalized according to the (8-N) rule. While Ba{sub 3}Sn{sub 2} reveals semiconducting behaviour, the germanides Ae{sub 7}Ge{sub 6} (Ae=Ca, Sr, and Ba) show metallic properties and a considerable {pi}-bonding character between the Ge atoms of the four-membered chains and the dumbbells. Highlights: Black-Right-Pointing-Pointer The germanides Sr{sub 7}Ge{sub 6} and Ba{sub 7}Ge{sub 6} as well as the stannide Ba{sub 3}Sn{sub 2} have been synthesized. Black-Right-Pointing-Pointer In Sr{sub 7}Ge{sub 6} and Ba{sub 7}Ge{sub 6} the Ge atoms are arranged as dumbbells and four-membered atom chains. Black-Right-Pointing-Pointer Ba{sub 3}Sn{sub 2} presents Sn{sub 2} dumbbells as a main structural motif. Black-Right-Pointing-Pointer The chemical bonding situation within these structures is discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRSDate not supplied

A Methodology for Reliability Assessments of Arbitrary Satellite Constellations

The commercial success of small satellite development and multi-satellite missions has led to constellation missions being proposed in every sector of the market. This paradigm shift has the potential to enable more capable and cost-effective space science missions. However, these novel approaches to space missions have outstripped existing policy and analysis methods for assessing the reliability of multi-satellite missions. Mission designers and decisionmakers need new methods and standards for modeling how the reliability of constituent spacecraft elements affect the aggregate reliability of constellations across a wide range of concepts and application-specific requirements. The Space Mission Analysis Branch at NASA’s Langley Research Center has developed a methodology for simulating the on-orbit reliability of arbitrary spacecraft constellations. In this paper, the authors describe the methodology and provides examples of how it can be used to evaluate specific constellation designs. To demonstrate the flexibility of the approach, several different constellation configurations are considered, including both homogenous and heterogenous designs. Next, the authors demonstrate the ability to perform broad parameter sweeps to develop greater insight into the intrinsic reliability trends associated with constellation concepts. Finally, the authors provide tables and novel data graphics which enable decisionmakers to quickly discern the relationships between constellation sizes, topologies, replenishment strategies, and overall constellation reliability.

satellite↗
DOE OSTI2018

Uncovering anisotropic magnetic phases via fast dimensionality analysis

A quantitative geometric predictor for the dimensionality of magnetic interactions is presented. This predictor is based on networks of superexchange interactions and can be quickly calculated for crystalline compounds of arbitrary chemistry, occupancy, or symmetry. The resulting data are useful for classifying structural families of magnetic compounds. We have examined compounds from a demonstration set of 42,520 materials with 3d transition metal cations. The predictor reveals trends in magnetic interactions that are often not apparent from the space group of the compounds, such as triclinic or monoclinic compounds that are strongly 2D. We present speci c cases where the predictor identi es compounds that should exhibit competition between 1D and 2D interactions, and how the predictor can be used to identify sparsely-populated regions of chemical space with as-yet-unexplored topologies of speci c 3d magnetic cations. The predictor can be accessed for the full list of compounds using a searchable frontend, and further information on the connectivity, symmetry, valence, and cation-anion and cation-cation coordination can be freely exported.

36 MATERIALS SCIENCE↗
DOE OSTI2013

COMPARISON BETWEEN PATH LENGTHS TRAVELED BY SOLAR ELECTRONS AND IONS IN GROUND-LEVEL ENHANCEMENT EVENTS

We have examined the Wind/3DP/SST electron and Wind/EPACT/LEMT ion data to investigate the path length difference between solar electrons and ions in the ground-level enhancement (GLE) events in solar cycle 23. Assuming that the onset time of metric type II or decameter-hectometric (DH) type III radio bursts is the solar release time of non-relativistic electrons, we have found that within an error range of {+-}10% the deduced path length of low-energy ({approx}27 keV) electrons from their release site near the Sun to the 1 AU observer is consistent with the ion path length deduced by Reames from the onset time analysis. In addition, the solar longitude distribution and IMF topology of the GLE events examined are in favor of the coronal mass ejection-driven shock acceleration origin of observed non-relativistic electrons. We have also found an increase of electron path lengths with increasing electron energies. The increasing rate of path lengths is correlated with the pitch angle distribution (PAD) of peak electron intensities locally measured, with a higher rate corresponding to a broader PAD. The correlation indicates that the path length enhancement is due to the interplanetary scattering experienced by first arriving electrons. The observed path length consistency implies that the maximum stable time of magnetic flux tubes, along which particles transport, could reach 4.8 hr.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2002

The developmental segregation of posterior crista and saccular vestibular fibers in mice: a carbocyanine tracer study using confocal microscopy

The developmental segregation of gravistatic input mediated by saccular fibers and of angular acceleration input mediated by posterior crista (PC) fibers was analyzed for the first time in a developing mammal using carbocyanine dye tracing in fixed tissue. The data reveal a more extensive projection of either endorgan in 7-day-old mice (P7) than has previously been reported in adult mammals. While we confirm and extend many previous findings, we also describe a novel segregation of saccular and posterior crista fibers in the anterior half of the medial vestibular nucleus (Mv) not reported before. Our developmental analysis shows a progressive segregation of posterior crista and saccular fibers to their respective discrete projection areas between embryonic day 15 (E15) and birth (P0). Retention of overlap in young adult animals appears to reflect the early embryonic overlap found in most areas. The vestibular projection does not show a topological projection as has been described in many other sensory systems. We propose that the unique projection features of the vestibular endorgans may relate to the transformation of vestibular signals into a motor output in the three neuron reflex arc of the VOR, of which the primary vestibular projection constitutes the first leg.

NASA Discipline Developmental Biology↗
DOE OSTI2023

Superconductivity in electron-doped PbBi 2 ⁢Te 4

Single crystals of In-doped PbBi 2 ⁢Te 4 are synthesized via a conventional solid-state method. Chemical analysis and Hall measurements indicate that In replaces Pb, introducing n-type carriers, creating Pb 1–x ⁢In x ⁢Bi 2 ⁢Te 4 . A superconducting transition is observed with a maximum transition temperature around 2.06 K for Pb 1–x⁢ In x ⁢Bi 2 ⁢Te 4 . Field-dependent transport measurements reveal type-II superconductivity and yield a maximum upper critical field around 1.55 T. Thermodynamic data indicates bulk superconductivity in the BCS weak-coupling limit. Finally, our findings establish an ambient-pressure superconducting system in the AM 2 ⁢X 4 family, and doped PbBi 2 ⁢Te 4 as a promising platform for the study of topological superconductivity.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Assessment of Proton Deflectometry for Exploding Wire Experiments

This project provides the first demonstration of the application of proton deflectometry for the diagnosis of electromagnetic field topology and current-carrying regions in Z-pinch plasma experiments. Over the course of this project several milestones were achieved. High-energy proton beam generation was demonstrated on the short-pulse high-intensity Leopard laser, (10 Joules in ~350 femtoseconds, and the proton beam generation was shown to be reproducible. Next, protons were used to probe the electromagnetic field structure of short circuit loads in order to benchmark the two numerical codes, the resistive-magnetohydrodynamics (MHD) code, Gorgon, and the hybrid particle-in-cell code, LSP for the interpretation of results. Lastly, the proton deflectometry technique was used to map the magnetic field structure of pulsed-power-driven plasma loads including wires and supersonic jets formed with metallic foils. Good agreement between the modeling and experiments has been obtained. The demonstrated technique holds great promise to significantly improve the understanding of current flow and electromagnetic field topology in pulsed power driven high energy density plasmas. Proton probing with a high intensity laser was for the first time implemented in the presence of the harsh debris and x-ray producing z-pinch environment driven by a mega-ampere-scale pulsed-power machine. The intellectual merit of the program was that it investigated strongly driven MHD systems and the influence of magnetic field topology on plasma evolution in pulsed power driven plasmas. The experimental program involved intense field-matter interaction in the generation of the proton probe, as well as the generation of plasma subjected to 1 MegaGauss scale magnetic fields. The computational aspect included two well-documented codes, in combination for the first time to provide accurate interpretation of the experimental results. The broader impact included the support of 2 graduate students, one at UCSD and one at NTF, who were exposed to both the experimental physics work, the MHD and PIC modeling of the system. A first generation college undergraduate student was employed to assist in experiments and data analysis throughout the project. Data resulting from the research program were broadly disseminated by publication in scientific journals, and presentation at international and national conferences and workshops.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2005

Quadrant CFD Analysis of a Mixer-Ejector Nozzle for HSCT Applications

This study investigates the sidewall effect on flow within the mixing duct downstream of a lobed mixer-ejector nozzle. Simulations which model only one half-chute width of the ejector array are compared with those which model one complete quadrant of the nozzle geometry and with available experimental data. These solutions demonstrate the applicability of the half-chute technique to model the flowfield far away from the sidewall and the necessity of a full-quadrant simulation to predict the formation of a low-energy flow region near the sidewall. The quadrant solutions are further examined to determine the cause of this low-energy region, which reduces the amount of mixing and lowers the thrust of the nozzle. Grid resolution and different grid topologies are also examined. Finally, an assessment of the half-chute and quadrant approaches is made to determine the ability of these simulations to provide qualitative and/or quantitative predictions for this type of complex flowfield.

Yoder, Dennis A.↗
NASA NTRS1978

Physical conditions in the corona for a bipolar magnetic region

The S-056 X-ray data from Skylab are used to determine quantitative values for the coronal conditions characterizing a new bipolar magnetic region (BMR). In particular, the analysis includes: (1) the time variation of the total soft X-ray flux from the BMR as a function of time; (2) the temporal and spatial variation of the temperature and emission measure; (3) the variation with time of thermal energy density; (4) the (calculated) magnetic-field configuration and magnetic flux density in the corona; and (5) the temporal variation of the magnetic-field energy in the corona. Detailed comparisons are made between the configuration of X-ray features and the magnetic-field topology.

Vorpahl, J. A.↗
NASA NTRS2009

Investigation of Boundary Conditions for Flexible Multibody Spacecraft Dynamics

In support of both the Space Shuttle and International Space Station programs, a set of generic multibody dynamics algorithms integrated within the Trick simulation environment have addressed the variety of on-orbit manipulator simulation requirements for engineering analysis, procedures development and crew familiarization/training at the NASA Johnson Space Center (JSC). Enhancements to these dynamics algorithms are now being driven by a new set of Constellation program requirements for flexible multibody spacecraft simulation. One particular issue that has been discussed within the NASA community is the assumption of cantilever-type flexible body boundary conditions. This assumption has been commonly utilized within manipulator multibody dynamics formulations as it simplifies the computation of relative motion for articulated flexible topologies. Moreover, its use for modeling of space-based manipulators such as the Shuttle Remote Manipulator System (SRMS) and Space Station Remote Manipulator System (SSRMS) has been extensively validated against flight data. For more general flexible spacecraft applications, however, the assumption of cantilever-type boundary conditions may not be sufficient. This paper describes the boundary condition assumptions that were used in the original formulation, demonstrates that this formulation can be augmented to accommodate systems in which the assumption of cantilever boundary conditions no longer applies, and verifies the approach through comparison with an independent model previously validated against experimental hardware test data from a spacecraft flexible dynamics emulator.

Boundary-value problems↗
DOE OSTI2023

Two-Phase Turbulent Kinetic Energy Budget Computation in Co-Current Taylor Bubble Flow

Simulation of two-phase flows is relevant for reactor design and safety at normal operation or during accident scenarios. Often, the two-phase flow is in a regime in which slugs are formed or where the flow stratifies. Modeling such situations using standard single-phase Reynolds-averaged Navier-Stokes (RANS) turbulence models fails due to an overestimation of the eddy viscosity at the resolved two-phase interface. To solve this, an ad hoc turbulence damping term has been proposed in the literature that reduces the turbulence production locally at a two-phase interface, analogously to turbulence wall functions. However, this approach must be tailored to the specific setting and does not consider physical contributions such as surface tension or flow topology. Therefore, the problem of two-phase interfacial turbulence must be studied more in-depth. In this work, we consider co-current turbulent Taylor bubble flow using high-fidelity numerical simulation. The Basilisk code is used to simulate a Taylor bubble rising in a vertical pipe. By simulating the bubble in a moving frame of reference, we may study the turbulent kinetic energy (TKE) budgets ahead of the bubble, in its wake, and across the interface. The implementation of the TKE budget computation and the underlying averaging techniques are validated for the single-phase region ahead of the Taylor bubble using reference direct numerical simulation data. The analysis of the TKE budgets in the setting of Taylor bubble flow allows for the study of how turbulence behaves due to the presence of a two-phase interface and, in turn, supports the improvement of two-phase RANS models.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS2011

Cassini Observations of Plasmoid Structure and Dynamics: Implications for the Role of Magnetic Reconnection in Magnetospheric Circulation at Saturn

We survey the Cassini magnetometer data during the deep tail orbits in 2006, and find 34 direct encounters with plasmoids. They occur as single, isolated events but also in groups of two or more plasmoids as is frequently observed at Earth . We show a case study example of three such plasmoids over three hours, where we estimate an upper limit of 5.68 GWb of flux closure, and derive a reconnection rate over this interval of 526 kV. We show the results of a superposed epoch analysis of al1 34 plasmoids indicating that, on average, plasmoids at Saturn are approix.8 min in duration and they tend toward a loop-like, as opposed to flux rope-like topology, with little or no axial core magnetic field. Our analysis shows that plasmoids at Saturn are followed by an extended interval of the post-plasmoid plasma sheet (PPPS) lasting approx.58 min. The average open magnetic flux disconnected by the continued reconnet:tion following plasmoid formation that creates the PPPS is approx.3 GWb. We calculate expected recurrence rates for plasmoids, and compare these with a derived observational recurrence rate of one plasmoid every approx.2.4 days, explaining the reasons why the spacecraft has not observed as many plasmoids as we predict will be released. We conclude that the Cassini magnetometer measurements require a combination of Vasyliunas-type closed-flux plasma sheet and Dungey-type open-flux lobe reconnection to account for the observed properties of the plasmoids and PPPS in Saturn's magnetotail.

Jackman, C. M.↗
NASA NTRS2013

Comparison Between Path Lengths Traveled by Solar Electrons and Ions in Ground-Level Enhancement Events

We have examined the Wind/3DP/SST electron and Wind/EPACT/LEMT ion data to investigate the path length difference between solar electrons and ions in the ground-level enhancement (GLE) events in solar cycle 23. Assuming that the onset time of metric type II or decameter-hectometric (DH) type III radio bursts is the solar release time of non-relativistic electrons, we have found that within an error range of plus or minus 10% the deduced path length of low-energy (approximately 27 keV) electrons from their release site near the Sun to the 1 AU observer is consistent with the ion path length deduced by Reames from the onset time analysis. In addition, the solar longitude distribution and IMF topology of the GLE events examined are in favor of the coronal mass ejection-driven shock acceleration origin of observed non-relativistic electrons.We have also found an increase of electron path lengths with increasing electron energies. The increasing rate of path lengths is correlated with the pitch angle distribution (PAD) of peak electron intensities locally measured, with a higher rate corresponding to a broader PAD. The correlation indicates that the path length enhancement is due to the interplanetary scattering experienced by first arriving electrons. The observed path length consistency implies that the maximum stable time of magnetic flux tubes, along which particles transport, could reach 4.8 hr.

electrons↗
DOE OSTI2022

Data-Driven Operator Theoretic Methods for Phase Space Learning and Analysis

This paper uses data-driven operator theoretic approaches to explore the global phase space of a dynamical system. In this work, we defined conditions for discovering new invariant subspaces in the state space of a dynamical system starting from an invariant subspace based on the spectral properties of the Koopman operator. When the system evolution is known locally in several invariant subspaces in the state space of a dynamical system, a phase space stitching result is derived that yields the global Koopman operator. Additionally, in the case of equivariant systems, a phase space stitching result is developed to identify the global Koopman operator using the symmetry properties between the invariant subspaces of the dynamical system and time-series data from any one of the invariant subspaces. Finally, these results are extended to topologically conjugate dynamical systems; in particular, the relation between the Koopman tuple of topologically conjugate systems is established. The proposed results are demonstrated on several second-order nonlinear dynamical systems including a bistable toggle switch. Our method elucidates a strategy for designing discovery experiments: experiment execution can be done in many steps, and models from different invariant subspaces can be combined to approximate the global Koopman operator.

42 ENGINEERING↗