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Results for “Diffuse Scattering”

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 1,027 records · Page 57
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Self-diffusion of liquid deuterium hydride and liquid tritium

Here, we present a quasi-elastic neutron scattering study of liquid deuterium hydride carried out using the Disk Chopper Spectrometer at the National Institute of Standards and Technology. Under saturated vapor pressure, the self-diffusion constant of deuterium hydride obeys an Arrhenius law D = D 0 exp(-E A /k B T), where the prefactor D 0 is given by D 0 = 9.5 ± 1.2 Å 2 /ps and the activation energy is given by E A = 58 ± 2 K. We apply the quantum law of corresponding states to the known diffusion constants of the hydrogen isotopologues. From this application, we estimate that D 0 ≈ 9.1 Å 2 /ps and E A ≈ 75 K in liquid tritium. Young’s theory of quantum-mechanical effects in van der Waals fluids is shown to apply to the diffusion constants of the liquid hydrogens. Our results underscore the importance of nuclear quantum effects in shaping the properties and behavior of the hydrogen isotopologues.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

The Numerical Computation of Clear-Sky Transmittance and Reflectance of Solar Radiation for the Modeling of PV System Performance

Modeling of photovoltaics (PV) system performance requires numerical computation of plane-of-array (POA) irradiances that are influenced by atmospheric absorption and scattering. Clear-sky transmittance and reflectance of diffuse irradiance are essential for the understanding of solar radiation related to multiple reflection between land surface and clouds. This study analytically solves the radiative transfer equation for clear-sky conditions and numerically computes the transmittance and reflectance of diffuse irradiance as functions of the optical thickness of the atmosphere. The computation will be implemented in all-sky radiative transfer models to improve their computational efficiency.

14 SOLAR ENERGY↗
DOE OSTI2024

Multiple origins of extra electron diffractions in fcc metals

Diffuse intensities in the electron diffraction patterns of concentrated face-centered cubic solid solutions have been widely attributed to chemical short-range order, although this connection has been recently questioned. This article explores the many nonordering origins of commonly reported features using a combination of experimental electron microscopy and multislice diffraction simulations, which suggest that diffuse intensities largely represent thermal and static displacement scattering. A number of observations may reflect additional contributions from planar defects, surface terminations incommensurate with bulk periodicity, or weaker dynamical effects.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Prediction of Thermal Transport Properties of Materials with Microstructural Complexity

This project aims at overcoming the major obstacle standing in the way of progress in dynamic multiscale simulation, which is the lack of a concurrent atomistic-continuum method that allows phonons, heat and defects to pass through the atomistic-continuum interface. The research has led to the development of a concurrent atomistic-continuum (CAC) methodology for multiscale simulations of materials microstructural, mechanical and thermal transport behavior. Its efficacy has been tested and demonstrated through simulations of dislocation dynamics and phonon transport coupled with microstructural evolution in a variety of materials and through providing visual evidences of the nature of phonon transport, such as showing the propagation of heat pulses in single and polycrystalline solids is partially ballistic and partially diffusive. In addition to providing understanding on phonon scattering with phase interface and with grain boundaries, the research has contributed a multiscale simulation tool for understanding of the behavior of complex materials and has demonstrated the capability of the tool in simulating the dynamic, in situ experimental studies of nonequilibrium transient transport processes in material samples that are at length scales typically inaccessible by atomistically resolved methods.

36 MATERIALS SCIENCE↗
DOE OSTI2022

A Molecular Description of Hydrogel Forming Polymers for Cement-Based Printing Paste Applications

This research endeavors to link the physical and chemical characteristics of select polymer hydrogels to differences in printability when used as printing aids in cement-based printing pastes. A variety of experimental probes including differential scanning calorimetry (DSC), NMR-diffusion ordered spectroscopy (DOSY), quasi-elastic neutron scattering (QENS) using neutron backscattering spectroscopy, and X-ray powder diffraction (XRD), along with molecular dynamic simulations, were used. Conjectures based on objective measures of printability and physical and chemical-molecular characteristics of the polymer gels are emerging that should help target printing aid selection and design, and mix formulation. Molecular simulations were shown to link higher hydrogen bond probability and larger radius of gyration to higher viscosity gels. Furthermore, the higher viscosity gels also produced higher elastic properties, as measured by neutron backscattering spectroscopy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1973

Unsteady, combined radiation and conduction in an absorbing, scattering, and emitting medium.

The transient cooldown of a gray, absorbing, isotropic scattering, emitting, and conducting medium bounded by gray, diffusely emitting and reflecting parallel plates is considered. Numerical solutions are obtained for the initial boundary-value problem with a discontinuous decrease in temperature at one boundary. The quasi-steady equation of radiative transfer is solved using Gaussian quadrature and a matrix eigenvector technique together with explicit numerical solution of the unsteady energy equation. Temperature and energy flux distributions are presented for variations of optical thickness, boundary emissivity, albedo, and conduction-radiation parameter.

Weston, K. C.↗
NASA NTRS1973

Remote sensing of ocean current boundary layer

The author has identified the following significant results. A time series of the Loop Current in the Gulf of Mexico, covering an annual cycle of growth, spreading, and decay, has been obtained in synchronization with ERTS-1. Computer enhanced images, which are necessary to extract useful oceanic information, show that the current can be observed either by color or sea state effects associated with the cyclonic boundary. The color effect relates to the spectral variations in the optical properties of the water and its suspended particles, and is studied by radiative transfer theory. Significant oceanic parameters identified are: the probability of forward scattering, and the ratio of scattering to total attenuation. Several spectra of upwelling diffuse light are computed as a function of the concentration of particles and yellow substance. These calculations compare favorably with experimental measurements and show that the ratio of channels method gives ambiguous interpretative results. These results are used to discuss features in images where surface measurements were obtained and are extended to tentative explanation in others.

Maul, G. A.↗
NASA NTRS1974

Remote sensing of ocean currents

The author has identified the following significant results. A time series of the Loop Current in the Gulf of Mexico, covering an annual cycle of growth, spreading, and decay, has been obtained in synchronization with ERTS-1. Computer enhanced images, which are necessary to extract useful oceanic information, show that the current can be observed either by color or sea state effects associated with the cyclonic boundary. The color effect relates to the spectral variations in the optical properties of the water and its suspended particles, and is studied by radiative transfer theory. Significant oceanic parameters identified are: the probability of forward scattering, and the ratio of scattering to total attenuation. Several spectra of upwelling diffuse light are computed as a function of the concentration of particles and yellow substance. These calculations compare favorably with experimental measurements and show that the ratio of channels method gives ambiguous interpretative results. These results are used to discuss features in images where surface measurements were obtained and are extended to tentative explanation in others.

Maul, G. A.↗
NASA NTRS1977

Spatial distribution of Compton-produced X-ray flux from rich and regular clusters of galaxies

The spatial distribution of radio and X-ray fluxes from rich and regular clusters of galaxies is discussed. A diffusion model is investigated in which high-energy electrons are ejected from a point source at the center of the cluster. While diffusing out, the electrons lose energy by Compton scattering with the universal blackbody photons, thus producing the X-ray emission. Traversing intracluster magnetic fields, the electrons emit synchrotron radio emission. For the Coma cluster of galaxies good agreement is found between the observed and predicted X-ray counting-rate distribution for the Compton model. From the observed radio data a value of about 3 by 10 to the -8th power gauss is deduced for the average magnetic-field strength in the central region of Coma.

Rephaeli, Y.↗
NASA NTRS1992

The molecular hydrogen emission around L1551 IRS 5 - Shock-heated molecular gas at the base of the molecular outflow

Spatially resolved observations of the v = 1-0 S(1) molecular hydrogen emission toward L1551 IRS 5 using the grating spectrometer at KPNO are presented. The S(1) emission consists of a ridge component extending toward west along the optical jet from its peak on IRS 5 and a diffuse component which traces the innermost region of the cavity enclosed by the molecular outflow. The ridge component represents shock-heated molecular gas at the root of the optical jet. The diffuse component is too bright to be of scattered origin; it most likely arises from shock-heated gas within the cavity and could represent an acceleration process of the molecular outflow.

Yamashita, Takuya↗
NASA NTRS1997

A Balloon-Borne Cloud Condensation Nuclei Counter

A balloon-borne instrument was constructed for observations of vertical profiles of cloud condensation nucleus (CCN) concentrations, active at 1% supersaturation. Droplet concentration in the static thermal-gradient diffusion chamber is deduced from the amount of scattered laser light detected by a photodetector. The photodetector is calibrated using a video camera and computer system to count the number of droplets produced from NaCl aerosol. Preliminary data are available from nine early morning profiles obtained at Laramie, Wyoming, between June 1995 and January 1997. To complement the CCN measurements, instruments that measure condensation nuclei (CN) and aerosols with diameter greater than 0.30 micrometers (D(sub 0.3) were also included on the balloon package. CCN concentrations exhibited a general decrease from the surface to the top of the boundary layers, were generally uniform through well-mixed layers, and show variability above well-mixed layers. In general, the structure of the CCN profile appears to be closely related to the structure in the CN and D(sub 0.3) profiles. Summer profiles generally have CCN concentration greater than 200/cu cm up to 500 mbar, whereas winter profiles are less than 200/cu cm at all levels.

Delene, David J.↗
NASA NTRS1995

Hybrid Simulations of Interstellar Pickup Ion Acceleration at the Solar Wind Termination Shock

Hybrid (kinetic ion/fluid electron) simulations have been used to study self-consistently the injection and initial stages of acceleration of interstellar pickup ions at the solar wind termination shock. Results are presented from one-dimensional simulations of high Mach number oblique (40 deg-50 deg) shocks with a 10% population of interstellar pickup hydrogen. In these simulations, the pickup ions, the solar wind ions, the shock fields and the waves are all treated self-consistently. Pickup ions reflected by the shock excite large amplitude (DELTA.B / B approximately 0.3) upstream magnetosonic waves. These waves, in turn, scatter the pickup hydrogen, as expected in the diffusive shock acceleration process. The spectrum of excited waves broadens in time. We find that, for the parameters studied, the termination shock efficiently injects and accelerates the interstellar pickup hydrogen, and thus this work represents a microscopic verification of this anomalous cosmic ray injection mechanism. Comparison of injected fluxes from the simulations with Voyager fluxes extrapolated to the termination shock suggests that injection at the termination shock is probably greater than injection by interplanetary shocks. A study of accelerated pickup ion orbits shows that the energy gain comes predominantly from shock drift acceleration in the shock front, with the upstream waves aiding the acceleration by allowing multiple encounters with the shock.

Liewer, P. C.↗
DOE OSTI2015

Tailoring diffuse reflectance of inhomogeneous films containing microplatelets

We develop an analytical model for calculating the diffuse reflectance of inhomogeneous films containing aligned microplatelets with diameters much greater than the wavelength. The scattering parameters are derived by modeling the platelets as one-dimensional thin films, and the overall diffuse reflectance of the slab is calculated using the Kubelka-Munk model. Our model predicts that reflection minima and maxima arising from coherent interference within the platelets are preserved in the diffuse reflectance of the disordered slab. Experimental validation of the model is provided by reflectance measurements (0.3–15 μm) of a solid aerosol film of aligned hexagonal boron nitride platelets.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Investigation of Accessible Pore Structure Evolution under Pressurization and Adsorption for Coal and Shale Using Small-Angle Neutron Scattering

Pore structure is an important parameter to quantify the reservoir rock adsorption capability and diffusivity, both of which are fundamental reservoir properties to evaluate the gas production and carbon sequestration potential for coalbed methane (CBM) and shale gas reservoirs. In this study, we applied small-angle neutron scattering (SANS) to characterize the total and accessible pore structures for two coal and two shale samples. We carried out in situ SANS measurements to probe the accessible pore structure differences under argon, deuterated methane (CD 4 ), and CO 2 penetrations. The results show that the total porosity ranges between 0.25 and 5.8% for the four samples. Less than 50% of the total pores are accessible to CD 4 for the two coals, while more than 75% of the pores were found to be accessible for the two shales. This result suggests that organic matter pores tend to be disconnected compared to mineral matter pores. Argon pressurization can induce pore contraction because of the mechanical compression of the solid skeleton in both the coal and shale samples. Hydrostatic compression has a higher effect on the nanopores of coal and shale with a higher accessible porosity. Both methane and CO 2 injection can reduce the accessible nanopore volume due to a combination of mechanical compression, sorption-induced matrix swelling, and adsorbed molecule occupation. CO 2 has higher effects on sorption-induced matrix swelling and pore filling compared to methane for both the coal and shale samples. Gas densification and pore filling could occur at higher pressures and smaller pore sizes. In conclusion, the compression and adsorption could create nanopores in the San Juan coal and Marcellus shale drilled core but could have an opposite effect in the other samples, namely, the processes could damage the nanopores in the Hazleton coal and Marcellus shale outcrop.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2015

Internal dynamics of F-actin and myosin subfragment-1 studied by quasielastic neutron scattering

Various biological functions related to cell motility are driven by the interaction between the partner proteins, actin and myosin. To obtain insights into how this interaction occurs, the internal dynamics of F-actin and myosin subfragment-1 (S1) were characterized by the quasielastic neutron scattering measurements on the solution samples of F-actin and S1. Contributions of the internal motions of the proteins to the scattering spectra were separated from those of the global macromolecular diffusion. Analysis of the spectra arising from the internal dynamics showed that the correlation times of the atomic motions were about two times shorter for F-actin than for S1, suggesting that F-actin fluctuates more rapidly than S1. It was also shown that the fraction of the immobile atoms is larger for S1 than for F-actin. These results suggest that F-actin actively facilitates the binding of myosin by utilizing the more frequent conformational fluctuations than those of S1. - Highlights: • We studied the internal dynamics of F-actin and myosin S1 by neutron scattering. • The correlation times of the atomic motions were smaller for F-actin than for S1. • The fraction of the immobile atoms was also smaller for F-actin than for S1. • Our results suggest that mobility of atoms in F-actin is higher than that in S1. • We propose that high flexibility of F-actin facilitates the binding of myosin.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Optical properties of human colon tissues in the 350 – 2500 nm spectral range

We present the optical characteristics of the mucosa and submucosa of human colon tissue. The experiments are performed in vitro using a LAMBDA 950 spectrophotometer in the 350 – 2500 nm spectral range. The absorption and scattering coefficients and the scattering anisotropy factor are calculated based on the measured diffuse reflectance and total and collimated transmittance spectra using the inverse Monte Carlo method. (laser biophotonics)

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Self-similar Cosmic-Ray Transport in High-resolution Magnetohydrodynamic Turbulence

We study the propagation of cosmic rays (CRs) through a simulation of magnetohydrodynamic (MHD) turbulence at an unprecedented resolution of 10,240 3 . We drive turbulence that is subsonic and super-Alfvénic, characterized by δB rms /B 0 = 2. The high resolution enables an extended inertial range such that the Alfvén scale l A , where δB(l A ) ≈ B 0 , is well resolved. This allows us to properly capture how the cascade transitions from large amplitudes on large scales to small amplitudes on small scales. We find that sharp bends in the magnetic field are key mediators of particle transport even on small scales via resonant curvature scattering. We further find that particle scattering in the turbulence shows strong hints of self-similarity: (1) the diffusion has a weak energy dependence over almost two decades in particle energy, and (2) the particles’ random walk exhibits a broad power-law distribution of collision times such that the diffusion is dominated by the rarest, long-distance excursions. Our results suggest that large-amplitude MHD turbulence can provide efficient scattering over a wide range of CR energies and may help explain many CR observations above a ∼TeV: the flattening of the B/C spectrum, the hardening of CR primary spectra, and the weak dependence of arrival anisotropy on CR energy.

Kempski, Philipp [Princeton Univ., NJ (United Stat↗