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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 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Measurement and modeling of the multiwavelength optical properties of uncoated flame-generated soot

Optical properties of flame-generated black carbon (BC) containing soot particles were quantified at multiple wavelengths for particles produced using two different flames: a methane diffusion flame and an ethylene premixed flame. Measurements were made for (i) nascent soot particles,(ii) thermally denuded nascent particles, and (iii) particles that were coated and then thermally denuded, leading to the collapse of the initiallylacy, fractal-like morphology. The measured mass absorption coefficients(MACs) depended on soot maturity and generation but were similar between flames for similar conditions. For mature soot, here corresponding to particles with volume-equivalent diameters > ~ 160 nm, the MAC and absorption Ångström exponent (AAE) values were independent of particle collapse while the single-scatter albedo increased. The MAC values for these larger particles were also size-independent. The mean MAC value at 532 nm for larger particles was 9.1±1.1 m 2 g -1 , about 17 % higher than that recommended by Bond and Bergstrom (2006), and the AAE was close to unity. Effective, theory-specific complex refractive index(RI) values are derived from the observations with two widely used methods:Lorenz–Mie theory and the Rayleigh–Debye–Gans (RDG) approximation. Mietheory systematically underpredicts the observed absorption cross sections at all wavelengths for larger particles (with x >0.9 ) independent of the complex RI used, while RDG provides good agreement. (The dimensionless size parameter x = π d p / λ , where d p is particle diameter and λ is wavelength.) Importantly, this implies that the use of Mie theory within air quality and climate models, as is common, likely leads to under predictions in the absorption by BC, with the extent of underprediction depending on the assumed BC size distribution and complex RI used. We suggest that it is more appropriate to assume a constant,size-independent (but wavelength-specific) MAC to represent absorption by uncoated BC particles within models.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Evaluation of the new capture vapourizer for aerosol mass spectrometers (AMS) through laboratory studies of inorganic species

Aerosol mass spectrometers (AMSs) and Aerosol Chemical Speciation Monitors (ACSMs) commercialized by Aerodyne are widely used to measure the non-refractory species in submicron particles. With the standard vapourizer (SV) that is installed in all commercial instruments to date, the quantification of ambient aerosol mass concentration requires the use of the collection efficiency (CE) to correct for the loss of particles due to bounce. Thus, a new capture vapourizer (CV) has been designed to reduce the need for a bounce-related CE correction. Two high-resolution AMS instruments, one with a SV and one with a CV, were operated side by side in the laboratory. Four standard species, NH 4 NO 3 , NaNO 3 , (NH 4 ) 2 SO 4 and NH 4 Cl, which typically constitute the majority of the mass of ambient submicron inorganic species, are studied. The effect of vapourizer temperature ( T v ∼ 200–800 °C) on the detected fragments, CE and size distributions are investigated. A T v of 500–550 °C for the CV is recommended. In the CV, CE was identical (around unity) for more volatile species (e.g. NH 4 NO 3 ) and comparable to or higher than the SV for less-volatile species (e.g. (NH 4 ) 2 SO 4 ), demonstrating an improvement in CE for laboratory inorganic species in the CV. The detected relative intensities of fragments of NO 3 and SO 4 species observed with the CV are different from those observed with the SV, and are consistent with additional thermal decomposition arising from the increased residence time and multiple collisions. Increased residence times with the CV also lead to broader particle size distribution measurements than with the SV. A method for estimating whether pure species will be detected in AMS sizing mode is proposed. Production of CO 2 (g) from sampled nitrate on the vapourizer surface, which has been reported for the SV, is negligible for the CV for NH 4 NO 3 and comparable to the SV for NaNO 3. . We observe an extremely consistent fragmentation for ammonium compared to very large changes for the associated anions. Together with other evidence, this indicates that it is unlikely that a major fraction of inorganic species vapourizes as intact salts in the AMS.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Propagating information content: an example with advection

The mathematical algorithm to derive geophysical information from remote sensing observations is called a retrieval. The mathematics of many retrieval problems are ill-posed, and thus a priori information is used to help constrain the derived geophysical variable to realistic values. One quantity of interest, therefore, is the information content of the observation. Perfect information content in the observation would be achieved if the retrieval were able to capture any perturbation in the desired geophysical variable with the proper magnitude. Many new data products can be derived by combining geophysical variables retrieved from multiple different remote sensors. This paper explores, for the first time, how to derive the information content of these derived products. The approach uses traditional error propagation techniques to derive the uncertainty of the derived field twice, both when the observations are used in the retrieval and also when only the a priori information from each remote sensor is propagated. These two uncertainties are then used to provide an estimate of the information content of the derived geophysical variable. This study demonstrates how to propagate the uncertainties from six different instruments to provide the information content for water vapor and temperature advection. A multi-month analysis demonstrates that, in a mean sense, the information content for temperature advection is nearly unity for all heights below 700 m while, the information content for water vapor advection is somewhat more variable but still larger than 0.6 in the convective boundary layer.

Turner, David D. [National Oceanic and Atmospheric↗
DOE OSTI2020

Seawater pH reconstruction using boron isotopes in multiple planktonic foraminifera species with different depth habitats and their potential to constrain pH and <i>p</i>CO<sub>2</sub> gradients

Boron isotope systematics of planktonic foraminifera from core-top sediments and culture experiments have been studied to investigate the sensitivity ofδ11B of calcite tests to seawater pH. However, our knowledge of the relationship between δ11B and pH remains incomplete for many taxa. Thus, to expand the potential scope of application of this proxy, we report δ11B data for seven different species of planktonic foraminifera from sediment core tops. We utilize a method for the measurement of small samples of foraminifera and calculate the δ11B-calcite sensitivity to pH for Globigerinoides ruber, Trilobus sacculifer (sacc or without sacc), Orbulina universa, Pulleniatina obliquiloculata, Neogloboquadrina dutertrei, Globorotalia menardii, and Globorotalia tumida, including for unstudied core tops and species. These taxa have diverse ecological preferences and are from sites that span a range of oceanographic regimes, including some that are in regions of air–sea equilibrium and others that are out of equilibrium with the atmosphere. The sensitivity of δ11Bcarbonate to δ11Bborate (e.g., Δδ11Bcarbonate/Δδ11Bborate) in core tops is consistent with previous studies for T. sacculifer and G. ruber and close to unity for N. dutertrei, O. universa, and combined deep-dwelling species. Deep-dwelling species closely follow the core-top calibration fo rO. universa, which is attributed to respiration-driven microenvironments likely caused by light limitation and/or symbiont–host interactions. Our data support the premise that utilizing boron isotope measurements of multiple species within a sediment core can be utilized to constrain vertical profiles of pH andpCO2 at sites spanning different oceanic regimes, thereby constraining changes in vertical pH gradients and yielding insights into the past behavior of the oceanic carbon pumps.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

\(J/\psi \) and \(\psi (2S)\) Production in Small Systems with PHENIX

The suppression of the ψ(2S) nuclear modification factor has been seen as a trademark signature of final-state effects in large collision systems for decades. In small systems, deviations of the nuclear modification from unity had been attributed to cold nuclear matter effects until the observation of strong differential suppression of the ψ(2S) state in p/d+A collisions, which suggests the presence of final-state effects. Here in this paper, we present results of J/ψ and ψ(2S) measurements in the dimuon decay channel for p + p, p+Al, and p+Au collision systems at $\sqrt{s_{NN}}$ = 200 GeV. Key results include the nuclear modification factors R pA as a function of centrality and rapidity. The measurements are compared with shadowing and transport model predictions, as well as complementary measurements at LHC energies.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Experimental investigation of elemental and isotopic evaporation processes by laser heating in an aerodynamic levitation furnace

In this report we carried out evaporation experiments on a B-type calcium–aluminium-rich inclusion (CAI) melt in a gas-mixing aerodynamic levitation laser furnace, at 1873 K and an oxygen partial pressure of 10 -9.1 atm, for durations ranging from 60 to 600 s. Evaporation of SiO 2 and MgO follow the same trend as those observed in vacuum furnace experiments at the same temperature and starting composition, showing that their evaporation relative to one another from the melt is independent of pressure, oxygen fugacity, and hydrodynamical regime specific to the furnace. Isotopic ratios of Mg and Si in evaporation residues are used to derive fractionation factors of α 26/24 Mg vap-liq = 0.9906± 0.0004 and α 30/28 Si vap-lip = 0.9943±0.0003, which are both significantly closer to unity than those found for evaporation in a vacuum, which translates to less isotope fractionation. The residues are also less isotopically fractionated than expected for cases in which transport of the gas species away from the melt is diffusion-controlled at 1-atm. By analysing the flow regimes in our furnace, we find that advection by the levitating gas is the primary mode of mass transport away from the melt surface, as opposed to diffusion-limited transport in a vacuum or 1-atm tube furnace. A modified Hertz–Knudsen–Langmuir formulation accounts for this process, and shows that isotopic fractionation of both Si and Mg reflect a saturation factor (ratio of the pressure of the evaporating species to vapour saturation pressure) equal to 0.75. This is in perfect accord with recent measurements of Cu isotopic fractionation using a similar furnace. The fact that three elements (Mg, Si, Cu) with varying equilibrium vapour pressures, activity coefficients in the liquid, and diffusion coefficients in the gas have the same scaling behaviour to saturation pressure is a strong indication that the mechanism controlling evaporation is driven by the hydrodynamical regime imposed in the furnace. Therefore, this class of experiments can be used to constrain processes in which advection dominates over diffusion, such as (but not limited to) planetary ejecta, tektites, giant impacts, nebular condensation in a turbulent flow, or nuclear fallout material. Finally, the possibility to reach high temperatures (in excess of 3500 K) in this furnace allows it to be used to evaluate the activity coefficients of melt components in extreme conditions relevant to molten planetary interiors (i.e., magma oceans), with a specific focus on refractory elements.

58 GEOSCIENCES↗
NASA NTRS1965

Feedback oscillator functions as low-level pulse stretcher

Low trigger pulses of the pulse stretcher circuit are obtained by forward biasing the transistor oscillator. The loop gain is kept below unity and prevents free-running oscillation. Two parallel feedback loops improve the stretching capabilities.

Source record↗
NASA NTRS1965

The spectral dependence of lunar emissivity.

The radiance of the lunar surface in the 8.0 to 10.4 μ region of the infrared spectrum was measured as a function of wavelength with a resolution better than 0.2 μ. Measurements were taken from a high altitude station (elevation 11,500 feet) to minimize the corrections required for atmospheric absorption. The radiance values obtained after correction are not compatible with gray or blackbody radiation at any temperature. Emissivities calculated on the basis of a 120°C lunar surface temperature vary from near unity at 8.5 μ to 0.90–0.93 in the region from 10.0 to 10.4 μ.

Infrared spectrum↗
NASA NTRS1964

Final Report of the Goddard Summer Workshop Program in Measurement and Simulation of the Space Environments , 15 Jun. - 15 Sep. 1964

The titles of the papers in this section of the 1964 Summer Workshop Report might give the impression that there is little in common between them, that they represent endeavors in widely scattered areas by men working in isolation. But there is a strong thread of unity; none of the work was done in isolation without some cooperation at least from others of Team A or of the Goddard permanent staff. And some of the work was fully a team effort, the joint achievement of many participants. The purpose of this introduction is to show how each of these projects came to be started, and how these separate tasks fit into the long-range objectives of Goddard Space Flight Center and the National Aeronautics and Space Administration.

ENVIRONMENT SIMULATION↗
NASA NTRS1967

Statistical communication theory

Communication theory on discrete analysis of homomorphic deconvolution, and unity feedback of two state modulator configurations

COMMUNICATION THEORY↗
NASA NTRS1966

Vibrating-piston electrostatic field sensor.

Vibrating-piston electrostatic field sensor for Gemini program, examining design improvements including unity-feedback preamplifier, noise reduction devices, etc

ELECTROSTATIC FIELD↗