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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 1,711 records · Page 95
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Effect of Buoyancy on the Perfomance of Solar Air Collectors with Different Structures

In order to study the effect of buoyancy on the performance of solar air collector, the theoretical analysis and experimental tests of four solar air collectors with different structures under natural convection and mixed convection are carried out. The results show that the air temperature rise of the protrusion-corrugated plate air collector is the highest in the natural convection, which is 9.17 Chigher than that of the flat plate collector, and the air outlet velocity is 0.19 m/s, increasing by 16.88% than that of the flat plate collector. Observing the effects on the heat transfer performance of mixed convection, it can be found, in addition to the protrusion-corrugated plate air collector, the buoyancy plays a positive role on the other three solar air collectors in the upward flow, while the buoyancy plays a negative role on the other three solar air collectors in the downward flow, and the enhanced degree of the buoyancy to the corrugated plate air collector is the largest, while the enhancement degree of the flat plate collector is the least.

14 SOLAR ENERGY↗
NASA NTRS1990

Modelling of piezoelectric actuator dynamics for active structural control

The paper models the effects of dynamic coupling between a structure and an electrical network through the piezoelectric effect. The coupled equations of motion of an arbitrary elastic structure with piezoelectric elements and passive electronics are derived. State space models are developed for three important cases: direct voltage driven electrodes, direct charge driven electrodes, and an indirect drive case where the piezoelectric electrodes are connected to an arbitrary electrical circuit with embedded voltage and current sources. The equations are applied to the case of a cantilevered beam with surface mounted piezoceramics and indirect voltage and current drive. The theoretical derivations are validated experimentally on an actively controlled cantilevered beam test article with indirect voltage drive.

Hagood, Nesbitt W.↗
DOE OSTI2023

Effects of Co substitution on the structural and magnetic properties of Sr ( Ni 1 - x Co x ) 2 P 2

Although SrNi 2 P 2 adopts the common ThCr 2 Si 2 structure for T ≥ 325 K, being in an uncollapsed tetragonal state rather than a collapsed tetragonal version, it is a special case for the ThCr 2 Si 2 class: on cooling below 325 K it adopts a one-third collapsed orthorhombic phase where one out of every three P rows bonds across the Sr layers. On the other hand, SrCo 2 P 2 only exhibits the uncollapsed ThCr 2 Si 2 structure from room temperature down to 1.8 K. Regardless of their low-temperature structures, neither SrNi 2 P 2 nor SrCo 2 P 2 manifests magnetic transitions down to 50 mK and 2 K, respectively. In this work we report the effects of Co substitution in Sr(Ni 1 - x Co x ) 2 P 2 , which allows for tuning the transition between the one-third collapsed and the uncollapsed structure. We find a rapid decrease of the one-third collapsed structural transition temperature with increasing Co fraction, until reaching full suppression for x ≥ 0.1. Substitution levels in the range 0.11 ≤ x ≤ 0.58 show no signs of any transition down to 1.8 K in the magnetization or resistance measurements in the range 1.8 ≤ T ≤ 300 K. However, different magnetically ordered states emerge for x ≥ 0.65, and disappear for x ≥ 0.99, recovering the known paramagnetic properties of the parent compound SrCo 2 P 2 . Further, these results are summarized in a phase diagram, built upon the characterization by energy dispersive x-ray spectroscopy, x-ray diffraction, temperature-dependent resistance, and field- and temperature-dependent magnetization measurements done on single crystals with different Co fraction. Both the magnetic and structural properties are compared to other systems with ThCr 2 Si 2 structure that exhibit magnetic ordering and collapsed tetragonal transitions. The magnetic ordering and moment formation are well described by Takahashi's spin fluctuation theory of itinerant electron magnetism.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2026

Molecular dynamics based study on the effects of cation size on the local structure and diffusion in polymerized ionic liquids

We have used coarse-grained molecular dynamics simulations to understand the effect of cation size on ion diffusion in polymerized ionic liquids at temperatures well above the glass transition temperature of the polymers. We investigated dependencies of the diffusion constant on the cation radius and static dielectric constant and interpreted these results in terms of underlying structural changes, and decoupling phenomenon. We have found non-monotonic effects of the cation radius on the diffusion constant, with a maximum at an intermediate radius resulting from two different size dependent effects. Changes in the radial distribution functions characterizing spatial distribution of cations with respect to anions result in a monotonic increase in the coordination number. This yields an increase in the effective interaction energy as a function of cation radius, which can explain the decrease in the diffusion constant. This increase is counteracted at small cation radii by a corresponding increase in decoupling of cation and anion dynamics. In addition, the diffusion constant is found to increase on increasing the static dielectric constant for all radii of the cations. These results highlight the significant role of decoupling in designing polymerized ionic liquids with an enhanced diffusion constant of cations.

Gillespie, Colin [ORNL] (ORCID:0000000320287080)↗
DOE OSTI2019

Preferential Paths of Air-water Two-phase Flow in Porous Structures with Special Consideration of Channel Thickness Effects

Accurate understanding and predicting the flow paths of immiscible two-phase flow in rocky porous structures are of critical importance for the evaluation of oil or gas recovery and prediction of rock slides caused by gas-liquid flow. A 2D phase field model was established for compressible air-water two-phase flow in heterogenous porous structures. The dynamic characteristics of air-water two-phase interface and preferential paths in porous structures were simulated. The factors affecting the path selection of two-phase flow in porous structures were analyzed. Transparent physical models of complex porous structures were prepared using 3D printing technology. Tracer dye was used to visually observe the flow characteristics and path selection in air-water two-phase displacement experiments. The experimental observations agree with the numerical results used to validate the accuracy of phase field model. The effects of channel thickness on the air-water two-phase flow behavior and paths in porous structures were also analyzed. The results indicate that thick channels can induce secondary air flow paths due to the increase in flow resistance; consequently, the flow distribution is different from that in narrow channels. This study provides a new reference for quantitatively analyzing multi-phase flow and predicting the preferential paths of immiscible fluids in porous structures.

42 ENGINEERING↗
NASA NTRS2011

Evaluation of Lightning Induced Effects in a Graphite Composite Fairing Structure

Defining the electromagnetic environment inside a graphite composite fairing due to lightning is of interest to spacecraft developers. This paper is the first in a two part series and studies the shielding effectiveness of a graphite composite model fairing using derived equivalent properties. A frequency domain Method of Moments (MoM) model is developed and comparisons are made with shielding test results obtained using a vehicle-like composite fairing. The comparison results show that the analytical models can adequately predict the test results. Both measured and model data indicate that graphite composite fairings provide significant attenuation to magnetic fields as frequency increases. Diffusion effects are also discussed. Part 2 examines the time domain based effects through the development of a loop based induced field testing and a Transmission-Line-Matrix (TLM) model is developed in the time domain to study how the composite fairing affects lightning induced magnetic fields. Comparisons are made with shielding test results obtained using a vehicle-like composite fairing in the time domain. The comparison results show that the analytical models can adequately predict the test and industry results.

Trout, Dawn H.↗
DOE OSTI2021

Generation of the TSL for Zirconium Hydrides from Ab Initio Methods

Zirconium hydride (ZrHx) is a moderator material used in TRIGA and other reactors that may exist in multiple phases with varying stoichiometry, which include the δ phase and the ϵ phase. Current ENDF/B-VIII.0 ZrHx thermal scattering law (TSL) evaluations do not distinguish between phases. These sub-libraries were generated with the LEAPR module of NJOY using historic phonon spectra derived from a central force model and assume incoherent elastic scattering for both bound hydrogen and zirconium, which neglects the effects of crystal structures important for scattering from zirconium bound in ZrHx. In this work, the TSLs for hydrogen and zirconium bound in δ-ZrHx and ϵ-ZrH2 were generated from phonon spectra derived from modern ab initio lattice dynamics methods and ab initio molecular dynamics. Subsequently, TSLs for hydrogen and zirconium in ZrHx and ZrH2 were generated using the Full Law Analysis Scattering System Hub (FLASSH) code. The built-in generalized coherent elastic routine was used to generate the previously neglected elastic contribution from zirconium for this material. The present TSLs provide both a re-evaluation of the current ZrH sub-libraries and expansion of the set of TSLs available for the examination of neutrons in systems with zirconium hydride, permitting explicit treatment of δ and ϵ phases.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1990

Weak gravitational lensing due to large-scale structure of the universe

The effect of the large-scale structure of the universe on the propagation of light rays is studied. The development of the large-scale density fluctuations in the omega = 1 universe is calculated within the cold dark matter scenario using a smooth particle approximation. The propagation of about 10 to the 6th random light rays between the redshift z = 5 and the observer was followed. It is found that the effect of shear is negligible, and the amplification of single images is dominated by the matter in the beam. The spread of amplifications is very small. Therefore, the filled-beam approximation is very good for studies of strong lensing by galaxies or clusters of galaxies. In the simulation, the column density was averaged over a comoving area of approximately (1/h Mpc)-squared. No case of a strong gravitational lensing was found, i.e., no 'over-focused' image that would suggest that a few images might be present. Therefore, the large-scale structure of the universe as it is presently known does not produce multiple images with gravitational lensing on a scale larger than clusters of galaxies.

Jaroszynski, Michal↗
DOE OSTI2022

Multiscale Crystalline Structure of Confined Polypeptoid Films: The Effect of Alkyl Side Chain Branching

Here we report the effect of alkyl side chain branching on melt-recrystallization of nanoconfined polypeptoid films using poly(N-octyl glycine) (PNOG) and poly(N-2-ethyl-1-hexyl glycine) (PNEHG) as model systems. Upon cooling from the isotropic melt, confined PNOG molecules recrystallize into a near-perfect orthorhombic crystal structure with the board-like molecules stacked face-to-face in the substrate-parallel direction, resulting in long-range ordered wormlike lamellae that occupy the entire film. By contrast, rod-like PNEHG molecules bearing branched N-2-ethyl-1-hexyl side chains stack into a columnar hexagonal mesophase with their backbones oriented parallel to the substrates, forming micron-sized sheaf-like superstructures under confinement, exposing large areas of empty spaces in the film. These findings highlight the effect of alkyl side chain branching on the packing motif and multiscale crystalline structure of polypeptoids under a nanoconfined geometry.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Dissecting the structural heterogeneity of proteins by native mass spectrometry

Abstract A single gene yields many forms of proteins via combinations of posttranscriptional/posttranslational modifications. Proteins also fold into higher‐order structures and interact with other molecules. The combined molecular diversity leads to the heterogeneity of proteins that manifests as distinct phenotypes. Structural biology has generated vast amounts of data, effectively enabling accurate structural prediction by computational methods. However, structures are often obtained heterologously under homogeneous states in vitro. The lack of native heterogeneity under cellular context creates challenges in precisely connecting the structural data to phenotypes. Mass spectrometry (MS) based proteomics methods can profile proteome composition of complex biological samples. Most MS methods follow the “bottom‐up” approach, which denatures and digests proteins into short peptide fragments for ease of detection. Coupled with chemical biology approaches, higher‐order structures can be probed via incorporation of covalent labels on native proteins that are maintained at the peptide level. Alternatively, native MS follows the “top‐down” approach and directly analyzes intact proteins under nondenaturing conditions. Various tandem MS activation methods can dissect the intact proteins for in‐depth structural elucidation. Herein, we review recent native MS applications for characterizing heterogeneous samples, including proteins binding to mixtures of ligands, homo/hetero‐complexes with varying stoichiometry, intrinsically disordered proteins with dynamic conformations, glycoprotein complexes with mixed modification states, and active membrane protein complexes in near‐native membrane environments. We summarize the benefits, challenges, and ongoing developments in native MS, with the hope to demonstrate an emerging technology that complements other tools by filling the knowledge gaps in understanding the molecular heterogeneity of proteins.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1980

Studies of pressure oscillations in a research dump combustor

A coaxial research dump combustor was used to investigate the acoustic modes structure and its effect on the inlet shock system. Acoustic wave structure was determined including the amplitude, frequency, and phase as a function of position. Inlet shock position, shock displacement, shock displacement frequency, and phase relative to acoustic wave structure were also defined. All results were compared to with one dimensional modeling.

Schadow, K. C.↗
DOE OSTI2021

Examining the EMC effect using the ${F}_{2}^{n}$ neutron structure function

The persistently mysterious deviations from unity of the ratio of nuclear target structure functions to those of deuterium as measured in deep inelastic scattering (often termed the “EMC effect”) have become the canonical observable for studies of nuclear medium modifications to free nucleon structure in the valence regime. The structure function of the free proton is well known from numerous experiments spanning decades. The free neutron structure function, however, has remained difficult to access. Recently it has been extracted in a systematic study of the global data within a parton distribution function extraction framework and is available from the CTEQ–Jefferson Lab (CJ) Collaboration. Here, we leverage the latter to introduce a new method to study the EMC effect in nuclei by reexamining existing data in light of the the magnitude of the medium modifications to the free neutron and proton structure functions independently. From the extraction of the free neutron from world data, it is possible to examine the nuclear effects in deuterium and their contribution to our interpretation of the EMC effect. In this study, we observe that the ratio of the deuteron to the sum of the free neutron and proton structure functions has some x B and Q 2 dependencies that impact the magnitude of the EMC effect as typically observed. Specifically, different EMC slopes are obtained when data from different x B and Q 2 values are utilized. Furthermore, while a linear correlation persists between the EMC and short range correlation effects, the slope is modified when deuteron nuclear effects are removed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Forest stand and canopy development unaltered by 12 years of CO2 enrichment*

Abstract Canopy structure—the size and distribution of tree crowns and the spatial and temporal distribution of leaves within them—exerts dominant control over primary productivity, transpiration and energy exchange. Stand structure—the spatial arrangement of trees in the forest (height, basal area and spacing)—has a strong influence on forest growth, allocation and resource use. Forest response to elevated atmospheric CO2 is likely to be dependent on the canopy and stand structure. Here, we investigated elevated CO2 effects on the forest structure of a Liquidambar styraciflua L. stand in a free-air CO2 enrichment experiment, considering leaves, tree crowns, forest canopy and stand structure. During the 12-year experiment, the trees increased in height by 5 m and basal area increased by 37%. Basal area distribution among trees shifted from a relatively narrow distribution to a much broader one, but there was little evidence of a CO2 effect on height growth or basal area distribution. The differentiation into crown classes over time led to an increase in the number of unproductive intermediate and suppressed trees and to a greater concentration of stand basal area in the largest trees. A whole-tree harvest at the end of the experiment permitted detailed analysis of canopy structure. There was little effect of CO2 enrichment on the relative leaf area distribution within tree crowns and there was little change from 1998 to 2009. Leaf characteristics (leaf mass per unit area and nitrogen content) varied with crown depth; any effects of elevated CO2 were much smaller than the variation within the crown and were consistent throughout the crown. In this young, even-aged, monoculture plantation forest, there was little evidence that elevated CO2 accelerated tree and stand development, and there were remarkably small changes in canopy structure. Questions remain as to whether a more diverse, mixed species forest would respond similarly.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1969

some comments on the use of infrared radiometry for remote atmospheric probing

A critique is presented of the lead paper by L.D. Kaplan on infrared radiometry. The following topics are analyzed: the extent to which the desirable thermal resolution of the lower troposphere can be achieved, the effects of complex cloud structure on infrared data, the effective weighting function if linearization is possible, remote sounding from below the atmosphere, first-guess fields and operational techniques to blend satellite infrared data into a mix of data from various meteorological systems, a simple inversion procedure for thermal structure, and problems arising from cloud and haze layers of variable amount and emissivity.

Godson, W. L.↗
NASA NTRS1985

Effect of R(3+) ions on the structure and properties of lanthanum borate glasses

The present investigation of glass formation in the (mole percent) systems 25La2O3 (x)R2O3 (75-x)B2O3, where R = Al, Ga, and (25-x)La2O3 (x)Ln2O3 75B2O3, where Ln = Gd, Er, Y, notes that up to 25 mol pct Al2O3 or Ga2O3 can be substituted for B2O3, while no more than about 5 mol pct Ln2O3, substituted for La2O3, caused macro-phase separation. The substitution of either R2O3 or Ln2O3 in the lanthanum borate system changes the separation distance between adjacent B3O6 chains. The effect of this structural change on the molar volume, transformation temperature, thermal expansion coefficient, and transformation-range viscosity is discussed.

Chakraborty, I. N.↗
DOE OSTI2024

The BOSS bispectrum analysis at one loop from the Effective Field Theory of Large-Scale Structure

Abstract We analyze the BOSS power spectrum monopole and quadrupole, and the bispectrum monopole and quadrupole data, using the predictions from the Effective Field Theory of Large-Scale Structure (EFTofLSS). Specifically, we use the one loop prediction for the power spectrum and the bispectrum monopole, and the tree level for the bispectrum quadrupole. After validating our pipeline against numerical simulations as well as checking for several internal consistencies, we apply it to the observational data. We find that analyzing the bispectrum monopole to higher wavenumbers thanks to the one-loop prediction, as well as the addition of the tree-level quadrupole, significantly reduces the error bars with respect to our original analysis of the power spectrum at one loop and bispectrum monopole at tree level. After fixing the spectral tilt to Planck preferred value and using a Big Bang Nucleosynthesis prior, we measureσ 8 = 0.794 ± 0.037,h = 0.692 ± 0.011, and Ω m = 0.311 ± 0.010 to about 4.7%, 1.6%, and 3.2%, at 68% CL, respectively.This represents an error bar reduction with respect to the power spectrum-only analysis of about 30%, 18%, and 13% respectively. Remarkably, the results are compatible with the ones obtained with a power-spectrum-only analysis, showing the power of the EFTofLSS in simultaneously predicting several observables. We find no tension with Planck.

Astronomy & Astrophysics↗