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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

The Precision Segmented Reflector program - On-orbit thermal behavior of the Submillimeter Imager and Line Survey telescope

The Precision Segmented Reflector program and the Submillimeter Imager and Line Survey mission are overviewed. The temperature requirements, thermal design and environment, as well as the on-orbit thermal performance of a 3.65-m-diameter passively-cooled submillimeter-wavelength telescope are discussed, and focus is placed on the geometric and thermal mathematical models employed in the study. Attention is given to an inflatable space-rigidized sunshade protecting the primary mirror thermally and the highly elliptical orbit chosen to reduce heat input from the earth. Primary-reflector temperature predictions are shown to indicate that a large spatial gradient can exist and the magnitude of the gradient is a strong function of the telescope pitch angle. It is suggested that the cryostat outer-shell temperature may be further lowered with the introduction of a rectangular shield between a solar array and the cryostat.

Tsuyuki, G.↗
NASA NTRS2009

Evidence for Interhemispheric Coupling during the Unusual Northern Polar Summer Mesosphere of 2002

Data from the MaCWAVE MIDAS Rocket Program launched during July, 2002, from Andoya Rocket Range (ARR) in Norway have demonstrated that the temperature structure of the summer polar mesosphere during this period was atypical, at least above ARR. The summer polar mesopause region was warmer than normal and of shorter duration than for other years analyzed. Theoretical studies have since been published that imply that the abnormal characteristics of this polar summer were generated by unusual dynamical processes occurring in the southern polar winter hemisphere. We have used data from the SABER instrument aboard the NASA TIMED Satellite to study these characteristics on a global scale and compare them with the features observed in the ensuing seven years. For background, The TIMED Satellite was launched on December 7, 2001 to study the dynamics and energy of the mesosphere and lower thermosphere (MLT). The SABER instrument on TIMED is a limb scanning infrared radiometer designed to measure a large number of minor constituents as well as temperature of the MLT. In this study, we have investigated the temperature characteristics of the polar mesosphere as a function of spatial and temporal considerations. We have used the most recent SABER dataset (1.07) that includes the improved temperature retrievals in Earth polar regions, Weekly averages were used 10 make the comparisons between the winter and summer hemispheres. The unusually short polar summer in the northern hemisphere during 2002 is clearly defined by this analysis and is shown to be unique for the 7 years analyzed. Furthermore, the data analysis agrees with recent theoretical studies showing that this behavior is a result of anomalous heating events in the southern polar stratosphere. The time sequence of the coupling process, as predicted by recent theoretical models, is well defined in a sequence of weekly temperature contour maps measured by SABER.

Goldberg, Richard A.↗
DOE OSTI2022

Electric-Field-Induced Spatially Dynamic Heterogeneity of Solvent Motion and Cation Transference in Electrolytes

While electric fields primarily result in migration of charged species in electrolytic solutions, the solutions are dynamically heterogeneous. Solvent molecules within the solvation shells of the cation will be dragged by the field while free solvent molecules will not. Here we combine electrophoretic NMR measurements of ion and solvent velocities under applied electric fields with molecular dynamics simulations to interrogate different solvation motifs in a model liquid electrolyte. Measured values of the cation transference number $(t^0_+)$ agree quantitatively with simulation-based predictions over a range of electrolyte concentrations. Solvent-cation interactions strongly influence the concentration-dependent behavior of $t^0_+$. We identify a critical concentration at which most of the solvent molecules lie within solvation shells of the cations. The dynamic heterogeneity of solvent molecules is minimized at this concentration where $t^0_+$ is approximately equal to zero.

42 ENGINEERING↗
DOE OSTI2021

A predictive discrete-continuum multiscale model of plasticity with quantified uncertainty

Multiscale models of materials, consisting of upscaling discrete simulations to continuum models, are unique in their capability to simulate complex materials behavior. The fundamental limitation in multiscale models is the presence of uncertainty in the computational predictions delivered by them. In this work, a sequential multiscale model has been developed, incorporating discrete dislocation dynamics (DDD) simulations and a strain gradient plasticity (SGP) model to predict the size effect in plastic deformations of metallic micro-pillars. The DDD simulations include uniaxial compression of micro-pillars with different sizes and over a wide range of initial dislocation densities and spatial distributions of dislocations. An SGP model is employed at the continuum level that accounts for the size-dependency of flow stress and hardening rate. Sequences of uncertainty analyses have been performed to assess the predictive capability of the multiscale model. The variance-based global sensitivity analysis determines the effect of parameter uncertainty on the SGP model prediction. The multiscale model is then constructed by calibrating the continuum model using the data furnished by the DDD simulations. A Bayesian calibration method is implemented to quantify the uncertainty due to microstructural randomness in discrete dislocation simulations (density and spatial distribution of dislocations) on the macroscopic continuum model prediction (size effect in plastic deformation). Here, the outcomes of this study indicate that the discrete-continuum multiscale model can accurately simulate the plastic deformation of micro-pillars, despite the significant uncertainty in the DDD results. Additionally, depending on the macroscopic features represented by the DDD simulations, the SGP model can reliably predict the size effect in plasticity responses of the micropillars with below 10% of error.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Origin of spin-driven ferroelectricity and effect of external pressure on the complex magnetism of the 6⁢ H perovskite Ba 3 ⁢Ho⁢Ru 2⁢ O 9

The compound Ba 3 HoRu 2 O 9 magnetically orders at 50 K (T N1 ), followed by another complex magnetic ordering at 10.2 K (T N2 ). The second magnetic phase transition was characterized by the coexistence of two competing magnetic ground states associated with two different magnetic wave vectors (K 1 = 0.5 0 0 and K 2 = 0.25 0.25 0). The multiferroicity and magnetoelectric coupling were predicted below T N2 in these 4d-based materials. Here, in this work, we have discussed the origin of spin-driven ferroelectricity, which is not known yet, and the nature of magnetoelectric domains. We have investigated the compound through time-of-flight neutron diffraction, synchrotron x-ray diffraction (XRD), ac susceptibility, frequency-dependent complex dielectric spectroscopy, and dc magnetization under external pressure. We have demonstrated that the noncollinear structure involving two different magnetic ions, Ru (4d) and Ho (4f), breaks the spatial inversion symmetry via inverse Dzyaloshinskii-Moriya (DM) interaction through strong 4d-4f magnetic correlation, which shifts the oxygen atoms and results in nonzero polarization. Such an observation of inverse DM interaction from two different magnetic ions which cause ferroelectricity is rarely observed. The stronger spin-orbit coupling of 4d orbital might play a major role in creating DM interaction of noncollinear spins. We have systematically studied the spin and dipolar dynamics, which exhibit intriguing behavior with shorter coherence lengths of second magnetic phase associated with the k 2 wave vector. The results manifest the development of finite-size magnetoelectric domains instead of true long-range ordering, which justifies the experimentally obtained low value of ferroelectric polarization. The lattice parameters and volume show a sharp anomaly at T N2 obtained by analyzing the temperature-dependence XRD, which is consistent with the ferroelectric transition, predicting a noncentrosymmetric space group, $P\bar{6}2c$, for this compound. Furthermore, we have investigated the effect of external pressure on this complex magnetism. The result reveals an enhancement of ordering temperature by the application of external pressure (~1.6 K/GPa). The external pressure might favor stabilizing the magnetic ground state associated with second magnetic phase. Our study shows an unconventional mechanism of spin-driven ferroelectricity involving inverse DM interaction between Ru (4d) and Ho (4f) magnetic ions due to strong 4d-4f cross coupling.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

High Order Implicit Residual-Based Spatial Discretization Error Estimation for S N Neutron Transport

This work demonstrates our novel residual source spatial discretization error estimator (LeR/TEAD) for a DGFEM-1 discretization and assesses it along with two contemporary estimators, Ragusa and Wang's h -refinement estimator (RW) and Duo, Azmy, and Zikatanov's explicit residual-based estimator (DAZ), on a suite of Method of Manufactured Solutions (MMS) 2D problems and three realistic problem geometries. LeR/TE-AD is attractive because it directly estimates the local error in the angular flux, as opposed to a mere indicator of the error's behavior, on the same mesh and method order as the original numerical solution, thus typically being less computationally intensive than a refinement-based method. On the MMS suite, LeR/TE-AD consistently displayed a reduced performance versus its DGFEM-0 results in terms of accuracy and precision metrics, though it was not typically grossly inaccurate. This is attributed to the irregularities in the true solution across singular characteristics limiting the local accuracy of the numerical flux solution, leading to poor derivative approximations used in the residual approximations. The error transport problem then spreads the error in the residual to nearby cells, causing a greater degree of imprecision that did not afflict DAZ or RW. In testing the estimators on realistic problem geometries, however, LeR/TE-AD fared better. In practice, the true error is much larger in non-idealized geometries like in MMS, and a superlinear true solution means that RW and DAZ are not beneficially biased for DGFEM-1 error estimation. LeR/TE-AD was typically first or second in accuracy, primarily competing with RW, but the latter usually consumed 2-4 times the computational time as LeR/TE-AD, and requires a solution with four times as many unknowns. Furthermore, RW and LeR/TE-AD can be used to compute direct estimates of the error in any quantity of interest that is based on the angular ux solution, such as the fission rate density in a fuel pin, whereas DAZ requires a heuristic extension due to its norm-based nature.

97 MATHEMATICS AND COMPUTING↗
NASA NTRS1986

Strain accumulation and surface deformation along the San Andreas, California

Stressing and rupture of a locked zone adjacent to a creeping fault segment was studied with special reference to strength heterogeneity depthwise and along-strike. The resulting precursory temporal and spatial variations of surface strain rate profiles were compared to geodetic measurements on the San Andreas fault in central California. Crustal deformation in great California earthquake cycles was also studied with special reference to the temporal decay of strain rate observed since the 1957 and 1906 great earthquakes, and comtemporary surface strain rate and velocity profiles at several locations along the San Andreas. The effect of viscoelastic response in the deep aseismic shear zone on the surface deformation behavior was examined. Work was begun on a fundamental reformulation of the crustal deformation problem focusing on the crustal deformation process affected by deep aseismic slip as the slip zone progresses toward an instability and as deep seismic slip continues postseismically, the 3-D nature of the problem due to geometry and material heterogeneity, and the time-dependent source coming from the lithosphere/astenospheric coupling process.

Li, Victor C.↗
NASA NTRS1989

Optically addressed spatial light modulators by MBE-grown nipi MQW structures

Promising approaches for achieving optically addressed spatial light modulators (O-SLMs) are investigated based on combining nipi and multiple quantum well structures. Theoretical aspects of photooptic effects achievable in such structures are treated. Test structures are grown by molecular beam epitaxy using two material systems. (In,Ga)As/GaAs and (Al,Ga)As/GaAs. Experiments show large optically controlled modulation of the absorption coefficient in the quantum well layers, a log power dependence on the control signal, millisecond and shorter time response, and generally predictable behavior. The results are encouraging for several different O-SLM device structures proposed.

Maserjian, Joseph↗
NASA NTRS1997

Wave Number Selection for Incompressible Parallel Jet Flows Periodic in Space

The temporal instability of a spatially periodic parallel flow of an incompressible inviscid fluid for various jet velocity profiles is studied numerically using Floquet Analysis. The transition matrix at the end of a period is evaluated by direct numerical integration. For verification, a method based on approximating a continuous function by a series of step functions was used. Unstable solutions were found only over a limited range of wave numbers and have a band type structure. The results obtained are analogous to the behavior observed in systems exhibiting complexity at the edge of order and chaos.

Miles, Jeffrey Hilton↗
NASA NTRS2002

Convergence of limb, visceral, and vertical semicircular canal or otolith inputs onto vestibular nucleus neurons

The major goal of this study was to determine the patterns of convergence of non-labyrinthine inputs from the limbs and viscera onto vestibular nucleus neurons receiving signals from vertical semicircular canals or otolith organs. A secondary aim was to ascertain whether the effects of non-labyrinthine inputs on the activity of vestibular nucleus neurons is affected by bilateral peripheral vestibular lesions. The majority (72%) of vestibular nucleus neurons in labyrinth-intact animals whose firing was modulated by vertical rotations responded to electrical stimulation of limb and/or visceral nerves. The activity of even more vestibular nucleus neurons (93%) was affected by limb or visceral nerve stimulation in chronically labyrinthectomized preparations. Some neurons received non-labyrinthine inputs from a variety of peripheral sources, including antagonist muscles acting at the same joint, whereas others received inputs from more limited sources. There was no apparent relationship between the spatial and dynamic properties of a neuron's responses to tilts in vertical planes and the non-labyrinthine inputs that it received. These data suggest that non-labyrinthine inputs elicited during movement will modulate the processing of information by the central vestibular system, and may contribute to the recovery of spontaneous activity of vestibular nucleus neurons following peripheral vestibular lesions. Furthermore, some vestibular nucleus neurons with non-labyrinthine inputs may be activated only during particular behaviors that elicit a specific combination of limb and visceral inputs.

NASA Discipline Developmental Biology↗
NASA NTRS2013

Impact of Surface Roughness and Soil Texture on Mineral Dust Emission Fluxes Modeling

Dust production models (DPM) used to estimate vertical fluxes of mineral dust aerosols over arid regions need accurate data on soil and surface properties. The Laboratoire Inter-Universitaire des Systemes Atmospheriques (LISA) data set was developed for Northern Africa, the Middle East, and East Asia. This regional data set was built through dedicated field campaigns and include, among others, the aerodynamic roughness length, the smooth roughness length of the erodible fraction of the surface, and the dry (undisturbed) soil size distribution. Recently, satellite-derived roughness length and high-resolution soil texture data sets at the global scale have emerged and provide the opportunity for the use of advanced schemes in global models. This paper analyzes the behavior of the ERS satellite-derived global roughness length and the State Soil Geographic data base-Food and Agriculture Organization of the United Nations (STATSGO-FAO) soil texture data set (based on wet techniques) using an advanced DPM in comparison to the LISA data set over Northern Africa and the Middle East. We explore the sensitivity of the drag partition scheme (a critical component of the DPM) and of the dust vertical fluxes (intensity and spatial patterns) to the roughness length and soil texture data sets. We also compare the use of the drag partition scheme to a widely used preferential source approach in global models. Idealized experiments with prescribed wind speeds show that the ERS and STATSGO-FAO data sets provide realistic spatial patterns of dust emission and friction velocity thresholds in the region. Finally, we evaluate a dust transport model for the period of March to July 2011 with observed aerosol optical depths from Aerosol Robotic Network sites. Results show that ERS and STATSGO-FAO provide realistic simulations in the region.

textures↗
DOE OSTI2018

Active Galactic Nuclei and the Origin of IceCube's Diffuse Neutrino Flux

The excess of neutrino candidate events detected by IceCube from the direction of TXS 0506+056 has generated a great deal of interest in blazars as sources of high-energy neutrinos. In this study, we analyze the publicly available portion of the IceCube dataset, performing searches for neutrino point sources in spatial coincidence with the blazars and other active galactic nuclei contained in the Fermi 3LAC and the Roma BZCAT catalogs, as well as in spatial and temporal coincidence with flaring sources identified in the Fermi Collaboration's All-Sky Variability Analysis (FAVA). We find no evidence that blazars generate a significant flux of high-energy neutrinos, and conclude that no more than 5-15% of the diffuse flux measured by IceCube can originate from this class of objects. While we cannot rule out the possibility that TXS 0506+056 has at times generated significant neutrino emission, we find that such behavior cannot be common among blazars, requiring TXS 0506+056 to be a rather extreme outlier and not representative of the overall blazar population. The bulk of the diffuse high-energy neutrino flux must instead be generated by a significantly larger population of less-luminous sources, such as non-blazar active galactic nuclei.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Revisiting the first Sandia Fracture Challenge with transient deformation heating and strain localization considerations

In this study, we present a systematic experimental study and accompanying theoretical analysis of the dependence of ductile fracture on strain localization, strain hardening rates, deformation-induced thermal softening, and transient heat conduction under spatially uniform as well as spatially heterogeneous deformation. Spatially uniform cases are studied via standard dogbone shaped specimens subject to uniaxial tension. Spatially heterogeneous deformation is studied via the so-called Sandia Fracture Challenge (SFC) specimen, which is a standard compact tension specimen modified with three machined holes in front of a blunt notch. We utilize the same precipitation hardened martensitic stainless steel used in the first SFC experiments, i.e. 15-5 PH with an H1075 heat treatment. We also study 15-5 PH in Condition A and with the H900 heat treatment, each of which has a different hardening behavior and ductility. We find that the ductility does not correlate with the deformation to first crack initiation in the SFC specimen. Instead, hardening rates are better correlated. Moreover, a re-examination finds that an accurate calibration of the hardening rates is strongly correlated with accurate blind predictions of ductile fracture in the SFC specimens. Given that thermal softening can greatly affect hardening rates, we provided a thermographic analysis of deformation-induced heating and transient heat transfer in both the dogbone shaped samples and the SFC specimens. Transient heating in stainless steels is found to have first-order effects on the strain at the onset of necking, strain to fracture, as well as strain localization and ductile fracture in complex geometries even under so-called quasi-static loading rates.

42 ENGINEERING↗
DOE OSTI2020

Unconventional ferroelectricity in moiré heterostructures

Although all matter is composed of component particles, these particles can arrange themselves in various ways, giving rise to emergent phenomena that can be surprisingly rich and often cannot be understood by studying only the individual constituents. Discovering and understanding novel forms of emergence in quantum materials, especially in those where multiple degrees of freedom or energy scales are delicately balanced, is of great fundamental interest to condensed matter research. In this work, we report on the surprising observation of emergent ferroelectricity in graphene-based moiré heterostructures. Ferroelectric materials exhibit an electrically-switchable electric dipole, which is usually formed by spatial separation between the averaged centers of positive and negative charge within the unit cell. Based on this, it is difficult to imagine graphene, a material composed only of carbon atoms, exhibiting ferroelectricity. However, in this work, we indeed realize switchable ferroelectricity in Bernal-stacked bilayer graphene sandwiched between two hexagonal boron nitride (BN) layers. By introducing a moiré superlattice potential (via aligning bilayer graphene with the top and/or bottom BN crystals), we observe prominent and robust hysteretic behavior of the graphene resistance with an externally applied out-of-plane displacement field. Our systematic transport measurements reveal rich and striking response as a function of displacement field and electron filling, not previously observed in any 2D systems, and beyond the framework of conventional ferroelectrics. We further directly probe the ferroelectric polarization through a nonlocal monolayer graphene sensor. Our results suggest an unconventional, odd parity electronic ordering in the bilayer graphene/BN moiré system. This emergent moiré ferroelectricity may pave the way for ultrafast, programmable, and atomically thin carbon-based memory devices.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

A time-resolved, in-chamber x-ray pinhole imager for Z

We have commissioned a new time-resolved, x-ray imaging diagnostic for the Z facility. The primary intended application is for diagnosing the stagnation behavior of Magnetized Liner Inertial Fusion (MagLIF) and similar targets. We have a variety of imaging systems at Z, both time-integrated and time-resolved, that provide valuable x-ray imaging information, but no system at Z up to this time provides a combined high-resolution imaging with multi-frame time resolution; this new diagnostic, called TRICXI for Time Resolved In-Chamber X-ray Imager, is meant to provide time-resolved spatial imaging with high resolution. The multi-frame camera consists of a microchannel plate camera. A key component to achieving the design goals is to place the instrument inside the Z vacuum chamber within 2 m of the load, which necessitates a considerable amount of x-ray shielding as well as a specially designed, independent vacuum system. Here, a demonstration of the imaging capability for a series of MagLIF shots is presented. Predictions are given for resolution and relative image irradiance to guide experimenters in choosing the desired configuration for their experiments.

47 OTHER INSTRUMENTATION↗
DOE OSTI2023

Entanglement structures in quantum field theories: Negativity cores and bound entanglement in the vacuum

Here, the many-body entanglement between two finite (size-d) disjoint vacuum regions of noninteracting lattice scalar field theory in one spatial dimension, i.e., a (d A × d B ) mixed Gaussian continuous variable system, is locally transformed into a tensor-product core of (1 A × 1 B ) mixed entangled pairs. Accessible entanglement within these core pairs exhibits an exponential hierarchy and as such identifies the structure of dominant region modes from which vacuum entanglement could be extracted into a spatially separated pair of quantum detectors. Beyond the core, the remaining modes of the halo are determined to be AB separable in isolation, as well as separable from the core. However, state preparation protocols that distribute entanglement in the form of (1 A × 1 B ) mixed core pairs are found to require additional entanglement in the halo that is obscured by classical correlations. This inaccessible (bound) halo entanglement is found to mirror the accessible entanglement, but with a step behavior as the continuum is approached. It remains possible that alternate initialization protocols that do not utilize the exponential hierarchy of core-pair entanglement may require less inaccessible entanglement. Entanglement consolidation is expected to persist in higher dimensions and may aid classical and quantum simulations of asymptotically free gauge field theories, such as quantum chromodynamics.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS2011

Thermal Structure of Titan's Troposphere and Middle Atmosphere

The thermal structure of Titan's atmosphere is reviewed, with particular emphasis on recent Cassini-Huygens results. Titan's has a similar troposphere-stratosphere-mesosphere pattern like Earth, but with a much more extended atmosphere, because of the weaker gravity, and also much lower temperatures, because of its greater distance from the sun. Titan's atmosphere exhibits an unusually large range in radiative relaxation times. In the troposphere, these are long compared to seasonal time scales, but in the stratosphere they are much shorter than a season. An exception is near the winter pole, where the stratospheric relaxation times at 100-170 km become comparable to the seasonal time scale; at the warm stratopause, they are comparable to a Titan day. Hence, seasonal behavior in the troposphere should be muted, but significant in the stratosphere. This is reflected in the small meridional contrast observed in temperatures in the troposphere and the large stratospheric contrasts noted above. A surprising feature of the vertical profiles of temperature is the abrupt transition between these regimes in at high northern latitudes in winter, where the temperatures in the lower stratosphere exhibit a sudden drop with increasing altitude. This could be a radiative effect, not associated with spatial variations in gaseous opacity, but rather from an optically thick condensate at thermal-infrared wavelengths. A curious aspect of Titan's middle atmosphere is that the axis of symmetry of the temperature field is tilted by several degrees relative to the rotational axis of the moon itself. Whether this is driven by solar heating or gravitational perturbations is not known. Titan's surface exhibits weak contrasts in temperature, approximately 3 K in the winter hemisphere. At low latitudes, there is evidence of a weak nocturnal boundary layer on the morning terminator, which is not radiatively controlled, but can be explained in terms of vertical mixing with a small eddy viscosity.

Flasar, F. M.↗
DOE OSTI2020

Stabilizing Dendritic Electrodeposition by Limiting Spatial Dimensions in Nanostructured Electrolytes.

The tendency of metals to form uncontrolled dendritic morphologies during electrodeposition hinders the development of safe and reliable metal batteries. Multiphase nanostructured electrolytes can suppress dendritic growth if the mechanical modulus of the electrolyte is high relative to that of the metal or if the conducting channels are confined to nanoscale dimensions. Direct visualization and analysis of electrodeposition within polymeric nanostructures elucidates the structure-property relationships and mechanisms underlying the suppression of dendrite growth. Here, we fabricate precisely structured multiphase films composed of nanochannels of a polymeric electrolyte in a background of nonconductive polymer on top of coplanar electrodes. The devices enable imaging and analysis of electrodeposition behavior as a function of channel width by scanning electron microscopy. We find that electrodeposition is confined to individual conductive channels and that radial propagation of the dendritic morphology is suppressed in channels for which the width is smaller than the characteristic dendritic nucleation size.

Sharon, Daniel↗