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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 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Electronic Probing and Manipulation of Low-Dimensional Magnets (Final Report)

We investigate the effects of reduced dimensionality of nanomagnets on the dynamical properties at low temperatures where quantum effects such as confinement, coherence, decoherence, and environmental coupling may be important. The experimental focus is on low-temperature transport measurements of such nanomagnets and cryogenic preamplification, followed by theoretical modeling of magnetic dynamics. In addition, we explore quantum effects in magnetic dynamics for their potential as quantum sensors of spin. We are particularly interested in the regime of strong environmental coupling, where novel phases of magnetic matter such as spin-boson may develop. The key new results are improved signal-to-noise ratio of magnetic tunneling junctions through low temperature preamplification that enables us to find the spin-dependent component of the current noise; a new powerful technique to simulate magnetic dynamics in the quantum coherent regime using the master equation formalism; and, finally, experimental hint of a novel state of matter in rare-earth doped permalloy ferromagnetic samples.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Unraveling Hidden Order and Dynamics in a Heterogeneous Ferroelectric System Using Machine Learning

We uploaded two batches of datasets: Batch-a) Equilibrium dynamics at a constant temperature at zero electric-field, with one trajectory each for 4-different defect structures (i.e. SETs 1 to 4). Each trajectory has a time-step of 0.25 fs, and is run for 7775000 time-steps, with snapshots written out every 4 time-steps (i.e. every 1fs); and Batch-b) Non-Equilibrium dynamics at a constant temperature with the same 0.25 fs time-step, but data dumped every 500 times-steps (i.e. every 125fs) for each of the SETs. The total trajectory of each defect structure (i.e. each SETs 1 to 4) is 2800000 time-steps (5600 snapshots), with stepping of electric-field by 0.01 V/Ã…, after every 100,000 time-steps (i.e. every 200 snapshots), from E=0 to E=0.05 V/Ã… to E = -0.05 V/Ã… to E=0.05 V/Ã….

36 MATERIALS SCIENCE↗
DOE OSTI2022

Cooperative allostery and structural dynamics of streptavidin at cryogenic- and ambient-temperature

Multimeric protein assemblies are abundant in nature. Streptavidin is an attractive protein that provides a paradigm system to investigate the intra- and intermolecular interactions of multimeric protein complexes. Also, it offers a versatile tool for biotechnological applications. Here, we present two apo-streptavidin structures, the first one is an ambient temperature Serial Femtosecond X-ray crystal (Apo-SFX) structure at 1.7 Å resolution and the second one is a cryogenic crystal structure (Apo-Cryo) at 1.1 Å resolution. These structures are mostly in agreement with previous structural data. Combined with computational analysis, these structures provide invaluable information about structural dynamics of apo streptavidin. Collectively, these data further reveal a novel cooperative allostery of streptavidin which binds to substrate via water molecules that provide a polar interaction network and mimics the substrate biotin which displays one of the strongest affinities found in nature.

60 APPLIED LIFE SCIENCES↗
NASA NTRS1986

Global dynamics and thermal structure of Jupiter's atmosphere

Voyager flyby observations have yielded the first detailed maps of wind and temperature fields in the Jupiter atmosphere; these data indicate that Jupiter's zonal currents violate the barotropic instability criterion if they extend only a few scale heights below the cloud tops. Microwave observations at mm and cm wavelengths have probed the atmosphere down to a level of about 7 bars, thereby constraining horizontal and vertical thermal structure in a region of the atmosphere about which little was known. Temporal variations in the temperature field suggest that dynamical processes may be important in the establishment of tropopause structure on short time scales. Ground-based and Voyager observations have also indicated a hemispheric asymmetry in temperature in the upper stratosphere.

Flasar, F. M.↗
NASA NTRS1986

Global dynamics and thermal structure of Jupiter's atmosphere

Voyager flyby observations have yielded the first detailed maps of wind and temperature fields in the Jupiter atmosphere; these data indicate that Jupiter's zonal currents violate the barotropic instability criterion if they extend only a few scale heights below the cloud tops. Microwave observations at mm and cm wavelengths have probed the atmosphere down to a level of about 7 bars, thereby constraining horizontal and vertical thermal structure in a region of the atmosphere about which little was known. Temporal variations in the temperature field suggest that dynamical processes may be important in the establishment of tropopause structure on short time scales. Ground-based and Voyager observations have also indicated a hemispheric asymmetry in temperature in the upper stratosphere.

Flasar, F. M.↗
DOE OSTI2022

Combined Experimental and Computational Study of Molybdenum and Niobium for Nuclear Sensor Application

Due to their novel electromagnetic and thermal properties, molybdenum (Mo) and niobium (Nb) become optimal temperature sensor materials for nuclear energy applications. We leveraged voltage recorded during a heat ramp to tune a computational method to predict the Seebeck electromotive force (EMF) of Mo and Nb. Using a combined Density Functional Theory (DFT) and Boltzmann Transport Equations (BTE) method the voltage was predicted but did not include the effects of temperature on atomic structure. Combining Ab Initio Molecular Dynamics (AIMD) and BTE included temperature effects on structure optimization and yielded voltages in a good agreement with experiment. Lanthanum (La) and Phosphorus (P) additives in Mo and Nb, respectively, could increase the EMF compared to those of the pure metals. The presence of oxygen (O) in Mo increases the EMF while O in Nb slightly reduces the EMF. Furthermore, our studies suggested that heat treatment-induced structural changes that lead to a reduction in voltage occur not only at the mesoscale as previously understood but also at the atomic scale.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

A multi-wavelength streaked optical pyrometer for dynamic shock compression measurements above 2500 K

This work presents a concept and implementation of a calibrated streaked spectral pyrometer (SSP) temperature diagnostic used in dynamically driven shock experiments on a two-stage gas gun. This system relies upon measuring the total system response using a tunable monochromator, a NIST-traceable calibrated power meter, and a SSP. The diagnostic performance is validated against previously measured temperatures of shock driven z-cut quartz at 99 GPa and 93 GPa. The results are found to agree with the literature to within 5% and are discussed in this manuscript. The experimental setup utilizes measurements from multiple SSP systems per sample, providing several independent measurements and substantially increasing confidence in the extrapolated shock driven sample temperature.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

Effect of Temperature on Thrombogenicity Testing of Biomaterials in an In Vitro Dynamic Flow Loop System

To develop and standardize a reliable in vitro dynamic thrombogenicity test protocol, the key test parameters that could impact thrombus formation need to be investigated and understood. In this study, we evaluated the effect of temperature on the thrombogenic responses (thrombus surface coverage, thrombus weight, and platelet count reduction) of various materials using an in vitro blood flow loop test system. Whole blood from live sheep and cow donors was used to assess four materials with varying thrombogenic potentials: negative-control polytetrafluoroethylene (PTFE), positive-control latex, silicone, and high-density polyethylene (HDPE). Blood, heparinized to a donor-specific concentration, was recirculated through a polyvinyl chloride tubing loop containing the test material at room temperature (22–24°C) for 1 hour, or at 37°C for 1 or 2 hours. The flow loop system could effectively differentiate a thrombogenic material (latex) from the other materials for both test temperatures and blood species ( p < 0.05). However, compared with 37°C, testing at room temperature appeared to have slightly better sensitivity in differentiating silicone (intermediate thrombogenic potential) from the relatively thromboresistant materials (PTFE and HDPE, p < 0.05). These data suggest that testing at room temperature may be a viable option for dynamic thrombogenicity assessment of biomaterials and medical devices.

Engineering↗
DOE OSTI2026

MRV Challenge 3: velocity and passive scalar comparison in a 3D turbulent flow

The third iteration of a magnetic resonance velocimetry (MRV) challenge comparison activity consisting of 3D flow measurements for a turbulent flow in a water channel moving past centrally positioned cubic obstacles is reported. In this challenge iteration, MRV measurements are coupled with either temperature or concentration measurements to extend the diagnostic utility. Five research teams from around the world conducted the measurements on a single shared apparatus. The water channel included partial elements along the channel sidewalls that varied in height and precluded easy optical accessibility. In addition to a turbulent mainstream flow, a secondary flow entered the channel between the second and third cubic elements from a square injector hole at the channel bottom wall. The injector jet interacts with the mainstream flow and mixes turbulently as it advects downstream. For the selected flow regime and water solutions used as working fluids, the mixing of the higher temperature or concentration through the secondary flow with the mainstream flow satisfies the same dynamics so that both temperature and concentration fields behave as passive scalars and can be directly compared. The measurements are explained in detail by each participating team, and the results are interpolated onto a common grid and compared using line profiles, contour plots, and isosurfaces.

Benson, Mike [ORNL] (ORCID:000000023210116X)↗
DOE OSTI2021

Quasi-one-dimensional uniform spin- 1 2 Heisenberg antiferromagnet KNaCuP 2 O 7 probed by P 31 and Na 23 NMR

Here we present the structural and magnetic properties of KNaCuP 2 O 7 investigated via x-ray diffraction, magnetization, specific heat, and P 31 and Na 23 NMR measurements and complementary electronic structure calculations. The temperature-dependent magnetic susceptibility and P 31 NMR shift could be modeled very well by the uniform spin- 1 2 Heisenberg antiferromagnetic chain model with a nearest-neighbor interaction J / k B ≃ 58.7 K . The corresponding mapping using first-principles electronic structure calculations leads to J DFT / k B ≃ 59 K with negligibly small interchain couplings, further confirming that the system is indeed a one-dimensional uniform spin- 1 2 Heisenberg antiferromagnet. The diverging trend of NMR spin-lattice relaxation rates ( 1 / T 1 31 and 1 / T 1 23 ) implies the onset of a magnetic long-range ordering at around T N ≃ 1 K . From the value of T N , the average interchain coupling is estimated to be J ' / k B ≃ 0.28 K . Moreover, the NMR spin-lattice relaxation rates show the dominant contributions from uniform ( q = 0 ) and staggered ( q = ± π / a ) spin fluctuations in the high- and low-temperature regimes, respectively, mimicking one-dimensionality of the spin lattice. We have also demonstrated that 1 / T 1 31 in high temperatures varies linearly with 1 / H , reflecting the effect of spin diffusion on the dynamic susceptibility. The temperature-dependent unit cell volume could be described well using the Debye approximation with a Debye temperature of Θ D ≃ 294 K , consistent with the heat capacity data.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Enhanced energy conversion efficiency promoted by cavitation in gasoline direct injection

High-pressure direct fuel injection plays the most crucial role in energy conversion and improving engine combustion efficiency and emission. The optimization of turbulent and multiphase fuel injection has focused on controlling hydrodynamic parameters such as injection pressure. While the thermodynamic influence is often considered in the flash boiling situation, we inquire into how gasoline-type fuel’s hydro- and thermodynamic properties impact the injection dynamics by fuel-temperature induced cavitation. The turbulent and cavitating flows emanating from the direct-injection nozzle is visualized by ultrafast x-ray imaging with an unprecedented spatiotemporal resolution. The ultrafast liquid-fuel dynamics are dominated by injection pressure as well as fuel temperature through cavitation, an important thermodynamic parameter but often difficult to control in engine combustion. With the most direct and quantitative measurement, we discovered that the near-nozzle fuel-jet dynamics can be perfectly scaled by a single dimensionless parameter, cavitation number, particularly sensitive to the fuel temperature, in a wide operation range. This universal scaling shows that cavitation can be harnessed to elevate the pneumatic-hydraulic to kinetic energy conversion efficiency, critical for promoting fuel atomization and engine combustion performance. This enhancement effect will have even more impact on engine combustion using alternative low-emission fuels with higher saturated vapor pressure.

30 DIRECT ENERGY CONVERSION↗
NASA NTRS1991

Viscoelastic properties of addition-cured polyimides used in high temperature polymer matrix composites

The viscoelastic properties of an addition-cured polyimide, PMR-15, were evaluated through dynamic mechanical and stress relaxation testing. Below the glass transition temperature, the dynamic mechanical properties of the composites are strongly affected by the absorbed moisture in the resin. At temperature 20 C and more above the glass transition temperature, the storage modulus increases continuously with time, indicating that additional crosslinking is occurring in the resin. For resin moisture contents less than 2 percent, stress relaxation curves measured at different temperatures can be superimposed using horizontal shifts along the log(time) axis with only small shifts along the vertical axis.

Roberts, Gary D.↗
DOE OSTI2022

Low Thermal Conductivity in Heteroanionic Materials with Layers of Homoleptic Polyhedra

Although BiAgOSe, an analogue of a well-studied thermoelectric material BiCuOSe, is thermodynamically stable, its synthesis is complicated by the low driving force of formation from the stable binary and ternary intermediates. Here we have developed a “subtraction strategy” to suppress byproducts and produce pure phase BiAgOSe using hydrothermal methods. Electronic structure calculations and optical characterization show that BiAgOSe is an indirect bandgap semiconductor with a bandgap of 0.95 eV. The prepared sample exhibits lower lattice thermal conductivities (0.61 W·m –1 ·K –1 at room temperature and 0.35 W·m –1 ·K –1 at 650 K) than BiCuOSe. Further, lattice dynamical simulations and variable temperature diffraction measurements demonstrate that the low lattice thermal conductivity arises from both the low sound velocity and high phonon–phonon scattering rates in BiAgOSe. These in turn result primarily from the soft Ag–Se bonds in the edge-sharing AgSe 4 tetrahedra and large sublattice mismatch between the quasi-two-dimensional [Bi 2 O 2 ] 2+ and [Ag 2 Se 2 ] 2– layers. These results highlight the advantages of manipulating the chemistry of homoleptic polyhedra in heteroanionic compounds for electronic structure and phonon transport control.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2006

The Juno Mission to Jupiter

Origin: Determine O/H ratio (water abundance) and constrain core mass to decide among alternative theories of origin. Interior: Understand Jupiter's interior structure and dynamical properties by mapping its gravitational and magnetic fields Atmosphere: Map variations in atmospheric composition, temperature, cloud opacity and dynamics to depths greater than 100 bars at all latitudes. Magnetosphere: Characterize and explore the three-dimensional structure of Jupiter's polar magnetosphere and auroras.

Jupiter↗
DOE OSTI2022

Neutral Mode Dominates the Forced Global and Regional Surface Temperature Response in the Past and Future

Abstract Using a large suite of Green's function perturbation experiments, we construct the emergent dynamical operator for surface temperature and extract the most excitable mode. The leading mode turns out to be the most dominant mode excited by the climate forcing of doubling CO 2 , alone capturing 56% of the total spatial variances of the surface temperature response. The pattern of the leading mode is partly organized by the atmospheric annular modes in both hemispheres, and further modulated by the feedbacks from ocean circulations. Though derived from a single model, the leading mode can capture the spatio‐temporal variabilities of the global mean surface temperature over the past century in both the CMIP6 model simulations and observations. Moreover, the leading mode is most efficiently excited by radiative forcings from the midlatitude bands centered around 45°N and 25°S, where most human activities take place, suggesting the potency of human influence on the climate change.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Hydrogen Spillover Is Regulating Minority Rh 1 Active Sites on TiO 2 in Room-Temperature Ethylene Hydrogenation

The complicated dynamics of active sites on single-atom catalysts under reducing conditions limits their applications in hydrogenation reactions and mechanistic understanding. Herein, we report that on Rh 1 /TiO 2 , *H spillover during room-temperature ethylene hydrogenation hydroxylates and reduces TiO 2 , enhancing the intrinsic activity of Rh 1 by 9-fold. Spectroscopic and kinetic evidence suggests that the spillover of *H is suppressed by their facile reaction with C 2 H 4 , most of the spilled *H are nonreactive spectators, and >99% turnovers occur on a small subset (<20%) of exposed “active Rh 1 ”. Steady-state kinetics indicates competitive adsorption between H and C 2 H 4 , H 2 dissociation is the rate-determining step, and the apparent activation barrier (E a,app ) of the reaction is ~48 kJ/mol. The evolution of Rh 1 under H 2 was further tracked by spectroscopic and microscopic techniques at elevated temperatures. At 200 °C, more Rh 1 are exposed, but these Rh 1 are at least 5-fold less active than that of the “active Rh 1 ”. At 300 °C, Rh clusters derived from Rh 1 become the main active sites, shifting E a,app to 62 kJ/mol, characteristic of Rh nanoparticles. At ≥400 °C, larger and more active Rh particles in the strong metal–support interaction state are created. In conclusion, this work revealed the unexpected regulation effects of *H spillover on M 1 active sites under ambient conditions, differentiated the minority active M 1 sites, and demonstrated how the stability of M 1 under reducing atmospheres affects hydrogenation catalysis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2004

Optical Diagnostic System for Solar Sails: Phase 1 Final Report

NASA's In-Space Propulsion program recently selected AEC-ABLE Engineering and L'Garde, Inc. to develop scale-model solar sail hardware and demonstrate its functionality on the ground. Both are square sail designs with lightweight diagonal booms (<100 g/m) and ultra-thin membranes (<10 g/sq m). To support this technology, the authors are developing an integrated diagnostics instrumentation package for monitoring solar sail structures such as these in a near-term flight experiment. We refer to this activity as the "Optical Diagnostic System (ODS) for Solar Sails" project. The approach uses lightweight optics and photogrammetric techniques to measure solar sail membrane and boom shape and dynamics, thermography to map temperature, and non-optical sensors including MEMS accelerometers and load cells. The diagnostics package must measure key structural characteristics including deployment dynamics, sail support tension, boom and sail deflection, boom and sail natural frequencies, sail temperature, and sail integrity. This report summarizes work in the initial 6-month Phase I period (conceptual design phase) and complements the final presentation given in Huntsville, AL on January 14, 2004.

Pappa, Richard S.↗