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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 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Interplay of confinement and surface energetics in the interaction of water with a metal–organic framework

Here, the enthalpy of water adsorption (Δh) on the metal–organic framework (MOF) HKUST-1 has been determined directly by calorimetry. The most exothermic value of Δh [–119.4 ± 0.5 kJ/(mol of water)] occurs at zero coverage and perhaps represents water confinement in the smallest (4-Å) cages. An intermediate Δh value of –50.2 ± 1.8 kJ/(mol of water) at higher loading probably corresponds to the binding of water on the available Cu nodes and subsequent filling of the largest (11-Å) pores. The weakest interactions take place in the medium (10-Å) cages, showing weak inclusion of water clusters in a limited hydrophobic environment. By combining ethanol adsorption calorimetry, mathematical analysis of the slope of the water adsorption isotherm, and the differential enthalpy of water adsorption curve, we are able not only to develop an approach to separate energetically multistage guest–host interactions in complex MOF architectures but also to distinguish a sequence of interactions with very similar energetic effects.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Polymerization of Terminal Acetylenes by a Bulky Monophosphine-Palladium Catalyst

A well-defined palladium complex [(tBuXPhos)Pd(Me)(BAr f )] bearing a bulky monophosphine ligand was synthesized and fully characterized. X-ray diffraction analysis shows that the 1,3,5-triisopropylaryl group of the dialkylbiaryl phosphine ligand exhibits a weak η 6 -interaction with the Pd(II) center. This catalyst exhibits excellent functional group tolerance and polymerizes propargyl esters containing benzoyl and acetyl groups, propargyl methyl ether, propargyl alcohol, benzyl acetylene, and phenyl acetylene to yield polymers with M n values in the range of 5–15 kDa with monomodal molecular weight distributions between ca. 1.4 and 2.1.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

The source of the threading dislocation in GaSb/GaAs hetero-structures and their propagation mechanism

The misfit and threading dislocations during GaSb epitaxy on GaAs substrate were investigated by weak beam dark field and high angle dark field scanning transmission electron microscopy. The geometric phase analysis and dislocation density tensor analysis were next used to analyze the strain around the threading dislocations and quantify the corresponding Burgers vectors. It is shown that there are three types of threading dislocations (mixed, edge, and pair of mixed types) close to the interface, which originate from the 60 Degree-Sign , Lomer, and 60 Degree-Sign pair misfit dislocations, respectively. During the growth of the epitaxial layer, the edge type as well as the pair of mixed threading dislocations split into two mixed type dislocations for the glide in {l_brace}111{r_brace} planes. Eventually, only mixed type dislocations have been observed at the surface of thick GaSb layers.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Charge symmetry breaking and parity violating electron scattering

I review the effects of charge symmetry breaking CSB on electromagnetic form factors and how that influences extraction of information regarding nucleon strangeness content and the weak mixing angle. It seems that CSB effects are very modest and should not impact the analysis of experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

The role of higher-order modes on the electromagnetic whistler-cyclotron wave fluctuations of thermal and non-thermal plasmas

Two fundamental challenging problems of laboratory and astrophysical plasmas are the understanding of the relaxation of a collisionless plasmas with nearly isotropic velocity distribution functions and the resultant state of nearly equipartition energy density with electromagnetic plasma turbulence. Here, we present the results of a study which shows the role that higher-order-modes play in limiting the electromagnetic whistler-like fluctuations in a thermal and non-thermal plasma. Our main results show that for a thermal plasma the magnetic fluctuations are confined by regions that are bounded by the least-damped higher order modes. We further show that the zone where the whistler-cyclotron normal modes merges the electromagnetic fluctuations shifts to longer wavelengths as the β{sub e} increases. This merging zone has been interpreted as the beginning of the region where the whistler-cyclotron waves losses their identity and become heavily damped while merging with the fluctuations. Our results further indicate that in the case of nonthermal plasmas, the higher-order modes do not confine the fluctuations due to the effective higher-temperature effects and the excess of suprathermal plasma particles. The analysis presented here considers the second-order theory of fluctuations and the dispersion relation of weakly transverse fluctuations, with wave vectors parallel to the uniform background magnetic field, in a finite temperature isotropic bi-Maxwellian and Tsallis-kappa-like magnetized electron–proton plasma. Our results indicate that the spontaneously emitted electromagnetic fluctuations are in fact enhanced over these quasi modes suggesting that such modes play an important role in the emission and absorption of electromagnetic fluctuations in thermal or quasi-thermal plasmas.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

A comparative study of lock-in-amplifiers and improved duffing chaotic oscillators for the detection and processing of weak signals

The measurement of multiphase flow parameters is of great importance in a wide range of industries. In the measurement of multiphase, the signals from the sensors are extremely weak and often buried in strong background noise. It is thus desirable to develop effective signal processing techniques that can detect the weak signal from the sensor outputs. In this paper, two methods, i.e., lock-in-amplifier (LIA) and improved Duffing chaotic oscillator are compared to detect and process the weak signal. For sinusoidal signal buried in noise, the correlation detection with sinusoidal reference signal is simulated by using LIA. The improved Duffing chaotic oscillator method, which based on the Wigner transformation, can restore the signal waveform and detect the frequency. Two methods are combined to detect and extract the weak signal. Simulation results show the effectiveness and accuracy of the proposed improved method. The comparative analysis shows that the improved Duffing chaotic oscillator method can restrain noise strongly since it is sensitive to initial conditions.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Quantifying charge resonance and multiexciton character in coupled chromophores by charge and spin cumulant analysis

We extend excited-state structural analysis to quantify the charge-resonance and multi-exciton character in wave functions of weakly interacting chromophores such as molecular dimers. The approach employs charge and spin cumulants which describe inter-fragment electronic correlations in molecular complexes. We introduce indexes corresponding to the weights of local, charge resonance, and biexciton (with different spin structure) configurations that can be computed for general wave functions thus allowing one to quantify the character of doubly excited states. The utility of the approach is illustrated by applications to several small dimers, e.g., He-H{sub 2}, (H{sub 2}){sub 2}, and (C{sub 2}H{sub 4}){sub 2}, using full and restricted configuration interaction schemes. In addition, we present calculations for several systems relevant to singlet fission, such as tetracene, 1,6-diphenyl-1,3,5-hexatriene, and 1,3-diphenylisobenzofuran dimers.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Two-component secular gravitational instability in a protoplanetary disk: A possible mechanism for creating ring-like structures

The instability in protoplanetary disks due to gas-dust friction and self-gravity of gas and dust is investigated using linear analysis. In the case where the dust-to-gas ratio is enhanced and turbulence is weak, the instability grows, even in gravitationally stable disks, on a timescale of order 10{sup 4-5} yr at a radius of order 100 AU. If we ignore the dynamical feedback from dust grains in the gas equation of motion, the instability reduces to the so-called ''secular gravitational instability'', which was investigated previously to be an instability of dust in a fixed background gas flow. In this work, we solve the equations of motion for both gas and dust consistently and find that long-wavelength perturbations are stable, in contrast to the secular gravitational instability in the simplified treatment. This may indicate that we should not neglect small terms in the equation of motion if the growth rate is small. The instability is expected to form ring structures in protoplanetary disks. The width of the ring formed at a radius of 100 AU is a few tens of AU. Therefore, the instability is a candidate for the formation mechanism of observed ring-like structures in disks. Another aspect of the instability is the accumulation of dust grains, and hence the instability may play an important role in the formation of planetesimals, rocky protoplanets, and cores of gas giants located at radii ∼100 AU. If these objects survive the dispersal of the gaseous component of the disk, they may be the origin of debris disks.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Dark matter search results from the PICO-60 CF 3 I bubble chamber

New data are reported from the operation of the PICO-60 dark matter detector, a bubble chamber filled with 36.8 kg of CF3I and located in the SNOLAB underground laboratory. PICO-60 is the largest bubble chamber to search for dark matter to date. With an analyzed exposure of 92.8 livedays, PICO-60 exhibits the same excellent background rejection observed in smaller bubble chambers. Alpha decays in PICO-60 exhibit frequency-dependent acoustic calorimetry, similar but not identical to that reported recently in a C3F8 bubble chamber. PICO-60 also observes a large population of unknown background events, exhibiting acoustic, spatial, and timing behaviors inconsistent with those expected from a dark matter signal. These behaviors allow for analysis cuts to remove all background events while retaining 48.2% of the exposure. Stringent limits on weakly interacting massive particles interacting via spin-dependent proton and spin-independent processes are set, and most interpretations of the DAMA/LIBRA modulation signal as dark matter interacting with iodine nuclei are ruled out.

PICO-60↗
DOE OSTI2024

Complex fermiology and electronic structure of antiferromagnet EuSnP

Throughout this work, we studied the electronic structure of a layered antiferromagnetic metal, EuSnP, in the paramagnetic and in the antiferromagnetic phase using angle-resolved photoemission spectroscopy (ARPES) alongside density-functional theory (DFT)-based first-principles calculations. The temperature dependence of the magnetic susceptibility measurements exhibits an antiferromagnetic transition at a Néel temperature of 21 K. Employing high-resolution ARPES, the valence-band structure was measured at several temperatures above and below the Néel temperature, which produced identical spectra independent of temperature. Through analysis of the ARPES results presented here, we attribute the temperature-independent spectra to the weak coupling of the Sn and P conduction electrons with Eu 4⁢ƒ states.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Effects of rapid thermal annealing on the properties of HfO{sub 2}/La{sub 2}O{sub 3} nanolaminate films deposited by plasma enhanced atomic layer deposition

In this work, HfO{sub 2}/La{sub 2}O{sub 3} nanolaminate films were deposited on Si substrates by plasma enhanced atomic layer deposition with in situ plasma treatment. Different annealing treatments were adopted to change films structure and performance. The upper HfO{sub 2} layers in HfO{sub 2}/La{sub 2}O{sub 3} nanolaminates were easily crystallized after annealing at 800 °C, while all the La{sub 2}O{sub 3} layers kept amorphous. X-ray photoelectron spectroscopy results indicated that LaO(OH) and La(OH){sub 3} peaks became weak, H{sub 2}O molecules in laminates evaporated during high-temperature annealing. Band diagram analysis showed that valence band offset and band gap widened after 800 °C annealing. Annealing, especially 800 °C annealing, had gentle effect on leakage current, but could obviously change capacitance and permittivity due to tetragonal and cubic phase formed in the HfO{sub 2} film.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Processes of diffusion in a limited ensemble of charged particles in a static magnetic field

The dynamics of a limited ensemble of charged particles in a spatially uniform static magnetic field has been studied analytically and numerically. Calculations have been performed for particles with various masses and charges in a wide range of the parameters of the systems under study. It has been shown that the transverse diffusion coefficient in an ensemble of particles in the magnetic field for weakly nonideal systems is described by the Townsend formula. Analytical estimates have been proposed for the analysis of the effective diffusion radius of the ensemble of particles owing to their thermal motion. The proposed relations have been tested by the numerical simulation of the problem.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Mass spectrum of vector mesons and their leptonic-decay constants in the bilocal relativistic potential model

A phenomenological model is developed in terms of bilocal meson fields in order to describe a vector meson and its leptonic decays. A new Salpeter equation for this particle and the Schwinger-Dyson equation allowing for the presence of an arbitrary potential and for a modification associated with the renormalization of the quark (antiquark ) wave function within the meson are given. An expression for the constant of the leptonic decay of the charged rho meson is obtained from an analysis of the decay process τ → ρν via parametrizing in it the hadronization of intermediate charged weak W bosons into a bilocal vector meson. The potential is chosen in the form of the sum of harmonic-oscillator and Coulomb potentials, and the respective boundary-value problem is formulated. It is shown that the solutions to this problem describe both the mass spectrum of vector mesons and their leptonic-decay constants.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Temperature of the Troposphere [in State of the Climate in 2018]

The 2018 annual global lower troposphere temperature (LTT; surface to ~10km) ranked third to seventh highest as monitored by radiosondes since 1958 and satellites since 1979 according to nine datasets examined for this analysis. (As noted in Section 2b1, the 2018 global average surface temperature was fourth highest.) A weak La Niña event extending into early 2018 suppressed the global LTT in the 2018 boreal winter and spring. In comparison, the tropical Pacific exhibited higher-than-average temperatures in boreal autumn, indicating the eventual initiation of a weak El Niño at the end of 2018 that contributed to higher-than-average temperatures in the following seasons in 2019. Among the nine datasets, the 2018 anomaly ranged from +0.23°C to +0.47°C relative to the 1981–2010 average and was ~0.3°C lower than the record warm year of 2016.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

femto-PIXAR: a self-supervised neural network method for reconstructing femtosecond X-ray free electron laser pulses

X-ray Free Electron Lasers (X-FELs) operate in a wide range of lasing configurations for a broad variety of scientific applications at ultrafast time-scales such as structural biology, materials science, and atomic and molecular physics. Shot-by-shot characterization of the X-FEL pulses is crucial for analysis of many experiments as well as tuning the X-FEL performance. However, for the weak pulses found in advanced configurations, e.g. those needed for coherent, two-pulse studies of quantum materials, there is no current method for reliably resolving pulse profiles. Here we show that a physics-based U-net model can reconstruct the individual pulse power profiles for sub-picosecond pulse separation without the need for simulations. Using experimental data from weak X-FEL pulse pairs, we demonstrate we can learn the pulse characteristics on a shot-by-shot basis when conventional methods fail.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Joint analyses of lensing, clustering, and galaxy clusters with DES and LSST (Early Career Award DE-SC0020247 Final Report)

Final technical report for Early Career Award DE-SC0020247 "Joint analyses of lensing, clustering, and galaxy clusters with DES and LSST". This report summarizes contributions to Dark Energy Survey analyses of weak lensing, clustering, and galaxy clusters, and contributions to the development of LSST-DESC cosmology analysis pipelines.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1972

Analysis of the failure of a polyester peripheral drive belt on the Mariner Mars 1971 flight tape recorder

A peripheral drive belt on the Mariner Mars 1971 tape recorder failed when a thin longitudinal strip separated off one edge. Analysis showed that the most probable cause of failure occurred from flexural fatigue initiating in mechanically weak locations which are introduced into the belt during fabrication. Methyl ethyl ketone, which is employed as a cleaning solvent during fabrication, was found to cause permanent reduction in engineering properties of polyester and could have contributed to the reduction of the fatigue resistance. Fatigue properties of the polyester drive belt are reviewed for the operating condition, as well as the sensitivity of polyester to cleaning solvents and the origin of mechanically weak locations.

Cuddihy, E. F.↗
NASA NTRS1974

Boundary layers in centrifugal compressors

The utility of boundary-layer theory in the design of centrifugal compressors is demonstrated. Boundary-layer development in the diffuser entry region is shown to be important to stage efficiency. The result of an earnest attempt to analyze this boundary layer with the best tools available is displayed. Acceptable prediction accuracy was not achieved. The inaccuracy of boundary-layer analysis in this case would result in stage efficiency prediction as much as four points low. Fluid dynamic reasons for analysis failure are discussed with support from flow data. Empirical correlations used today to circumnavigate the weakness of the theory are illustrated.

Dean, R. C., Jr.↗