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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Visible-light Phase Curves from the Second Year of the TESS Primary Mission

We carried out a systematic study of full-orbit phase curves for known transiting systems in the northern ecliptic sky that were observed during Year 2 of the TESS primary mission. We applied the same methodology for target selection, data processing, and light-curve fitting as we did in our Year 1 study. Out of the 15 transiting systems selected for analysis, seven—HAT-P-7, KELT-1, KELT-9, KELT-16, KELT-20, Kepler-13A, and WASP-12—show statistically significant secondary eclipses and day–night atmospheric brightness modulations. Small eastward dayside hot-spot offsets were measured for KELT-9b and WASP-12b. KELT-1, Kepler-13A, and WASP-12 show additional phase-curve variability attributed to the tidal distortion of the host star; the amplitudes of these signals are consistent with theoretical predictions. We combined occultation measurements from TESS and Spitzer to compute dayside brightness temperatures, TESS-band geometric albedos, Bond albedos, and phase integrals for several systems. The new albedo values solidify the previously reported trend between dayside temperature and geometric albedo for planets with 1500 K < T {sub day} < 3000 K. For Kepler-13Ab, we carried out an atmospheric retrieval of the full secondary eclipse spectrum, which revealed a noninverted temperature–pressure profile, significant H{sub 2}O and K absorption in the near-infrared, evidence for strong optical atmospheric opacity due to sodium, and a confirmation of the high geometric albedo inferred from our simpler analysis. We explore the implications of the phase integrals (ratios of Bond to geometric albedos) for understanding exoplanet clouds. We also report updated transit ephemerides for all of the systems studied in this work.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Visible to near-infrared spectral reflectance along the NGEE-Arctic tram transect, Utqiagvik (Barrow), Alaska, 2015-2018

Canopy spectral reflectance collected measured in 2015-2018 along the NGEE-Arctic tram located on the Barrow Environmental Observatory (BEO), Barrow, Alaska. Measurements were made using a PP-Systems UniSpec-DC spectrometer mounted on an automatically operated instrument cart. Spectra were collected at 137 stop points at 0.5 m intervals along the tram transect. Transect runs were collected daily, or multiple times per day, from April or May through to August or September each year. Downwelling radiance was measured using a 2 meter fiber optic cable connected to a cosine diffuser. Upwelling (i.e. reflected) radiance was measured using a 2 meter cable connected to a 12 degree field-of-view (FOV) lens. Canopy reflectance was calculated using the ratio of upwelling to downwelling radiance measured over a 99.99% reflectance Spectralon standard measured at the start of each measurement set. Unprocessed spectral data are presented in .spu files. Metadata are provided in csv files, and the instrument manual (pdf). The Next-Generation Ecosystem Experiments: Arctic (NGEE Arctic), was a 15-year research effort (2012-2027) to reduce uncertainty in Earth System Models by developing a predictive understanding of carbon-rich Arctic ecosystems and feedbacks to climate. NGEE Arctic was supported by the Department of Energy's Office of Biological and Environmental Research. The NGEE Arctic project had two field research sites: 1) located within the Arctic polygonal tundra coastal region on the Barrow Environmental Observatory (BEO) and the North Slope near Utqiagvik (Barrow), Alaska and 2) multiple areas on the discontinuous permafrost region of the Seward Peninsula north of Nome, Alaska. Through observations, experiments, and synthesis with existing datasets, NGEE Arctic provided an enhanced knowledge base for multi-scale modeling and contributed to improved process representation at global pan-Arctic scales within the Department of Energy's Earth system Model (the Energy Exascale Earth System Model, or E3SM), and specifically within the E3SM Land Model component (ELM).

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Silicon-based visible and near-infrared optoelectric devices

In one aspect, the present invention provides a silicon photodetector having a surface layer that is doped with sulfur inclusions with an average concentration in a range of about 0.5 atom percent to about 1.5 atom percent. The surface layer forms a diode junction with an underlying portion of the substrate. A plurality of electrical contacts allow application of a reverse bias voltage to the junction in order to facilitate generation of an electrical signal, e.g., a photocurrent, in response to irradiation of the surface layer. The photodetector exhibits a responsivity greater than about 1 A/W for incident wavelengths in a range of about 250 nm to about 1050 nm, and a responsivity greater than about 0.1 A/W for longer wavelengths, e.g., up to about 3.5 microns.

Mazur, Eric↗
DOE OSTI2021

Capped co-doped core/shell nanocrystals for visible light emission

In various embodiments the present disclosure provides a core/shell nanocrystal comprising a core and a shell formed on the core, wherein the core/shell nanocrystal is co-doped with at least one metal dopant and at least one trivalent cation. In some embodiments, the trivalent cation is a Group 13 element. Methods of making and using the core/shell nanocrystal are also described.

Zhang, Jin Z.↗
DOE OSTI2021

Power allocation for visible light communication

A system and method for providing optical multiple input and multiple output data communication using optical signals includes a plurality of light sources, a plurality of photodetectors, and at least one controller. The plurality of light sources are configured to emit optical signals to communicate data. The plurality of photodetectors are configured to sense the optical signals, and are embedded in at least one receiver. At least one of the plurality of photodetectors is configured to receive the optical signals from two or more of the plurality of light sources. The controller is configured to assign a transmit power to at least some of the plurality of light sources based on parameters of the plurality of photodetectors.

Brandt-Pearce, Maite↗
DOE OSTI2023

Community threat intelligence and visibility for operational technology networks

Techniques are provided for community threat intelligence for operational technology networks. For a plurality of OT networks, at least one monitoring device processes OT network traffic and collects telemetry data, and a telemetry sanitization system applies a sanitization process to the telemetry data to generate sanitized telemetry data that does not include sensitive data. A computer system receives sanitized telemetry data from the telemetry sanitization systems provided for the plurality of OT networks, maintains threat intelligence data generated based on the sanitized telemetry data, and provides access to at least one of the threat intelligence data and the sanitized telemetry data to a plurality of users.

Bladow, Garrett↗
DOE OSTI2019

Edge Dislocations Induce Improved Photocatalytic Efficiency of Colored TiO2

Titanium oxide is the most widely used material for photocatalytic applications due to its low cost and environmental friendliness. One of the grand challenges to improve its energy conversion efficiency is to utilize more visible light while inhibiting the recombination of photo-generated electrons and holes. We use a one-step hydro-solvothermal method to obtain colored ultra-fine nanowires of rutile and nanoparticles of anatase with edge dislocations, which induced broadened visible solar absorption (400-900 nm) and improved photocatalytic efficiency up to 1.8 times that of rutile or anatase without defects. Enhanced photocatalytic activity of these structures is demonstrated by photodegrading methylene blue measurements under simulated solar light irradiation. Results show the existence of Ti3+, induced by edge dislocations, and subsequent electronic band structure-property relationships. This work highlights a strategy for generating sufficient desired defects in TiO2 nanostructures, leading to broadened visible solar absorption and improved photocatalytic efficiency under visible light irradiation.

Ren, Peng↗
DOE OSTI2019

Networked-based Cyber Analysis using Deep Packet Inspection (DPI) for High-Speed Networks

Today’s networked systems utilize advanced security components such as Next Generation Firewall (NGFW), Intrusion Detection Systems (IDS), Intrusion Prevention Systems (IPS), and methods for network traffic classification. A fundamental aspect of these security components and methods is network packet visibility and packet inspection. To achieve packet visibility, a compute mechanism used by these security components and methods is Deep Packet Inspection (DPI). DPI is used to obtain visibility into packet fields by looking deeper inside packets, beyond just IP address, port, and protocol. However, DPI is considered extremely expensive in terms of compute processing costs and very challenging to implement on high speed network systems. The fundamental scientific paradigm addressed in this research project is the application of greater network packet visibility and packet inspection at data rates greater than 40Gbps to secure computer network systems. The greater visibility and inspection will enable detection of advanced content-based threats that exploit application vulnerabilities and are designed to bypass traditional security approaches such as firewalls and antivirus scanners. Greater visibility and inspection are achieved through identification of the application protocol (e.g., HTTP, SMTP, Skype) and, in some cases, extraction and processing of the information contained in the packet payload. Analysis is then performed on the resulting DPI data to identify potentially malicious behavior. In order to obtain visibility and inspect the application protocol and contents at high speed data rates, advanced DPI technologies and implementations are developed.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2022

Invisible ship tracks show large cloud sensitivity to aerosol

Cloud reflectivity is sensitive to atmospheric aerosol concentrations because aerosols provide the condensation nuclei on which water condenses. Increased aerosol concentrations due to human activity affect droplet number concentration, liquid water and cloud fraction, but these changes are subject to large uncertainties. Ship tracks, long lines of polluted clouds that are visible in satellite images, are one of the main tools for quantifying aerosol–cloud interactions. However, only a small fraction of the clouds polluted by shipping show ship tracks. Here we show that even when no ship tracks are visible in satellite images, aerosol emissions change cloud properties substantially. We develop a new method to quantify the effect of shipping on all clouds, showing a cloud droplet number increase and a more positive liquid water response when there are no visible tracks. We directly detect shipping-induced cloud property changes in the trade cumulus regions of the Atlantic, which are known to display almost no visible tracks. Our results indicate that previous studies of ship tracks were suffering from selection biases by focusing only on visible tracks from satellite imagery. The strong liquid water path response we find translates to a larger aerosol cooling effect on the climate, potentially masking a higher climate sensitivity than observed temperature trends would otherwise suggest.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

ALICE luminosity determination for Pb–Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV

Luminosity determination within the ALICE experiment is based on the measurement, in van der Meer scans, of the cross sections for visible processes involving one or more detectors (visible cross sections). In 2015 and 2018, the Large Hadron Collider provided Pb–Pb collisions at a centre-of-mass energy per nucleon pair of $\sqrt{s_{NN}}$ = 5.02 TeV. Two visible cross sections, associated with particle detection in the Zero Degree Calorimeter (ZDC) and in the V0 detector, were measured in a van der Meer scan. This article describes the experimental set-up and the analysis procedure, and presents the measurement results. The analysis involves a comprehensive study of beam-related effects and an improved fitting procedure, compared to previous ALICE studies, for the extraction of the visible cross section. The resulting uncertainty of both the ZDC-based and the V0-based luminosity measurement for the full sample is 2.5%. The inelastic cross section for hadronic interactions in Pb–Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV, obtained by efficiency correction of the V0-based visible cross section, was measured to be 7.67 ± 0.25 b, in agreement with predictions using the Glauber model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Control of optical absorption and fluorescence spectroscopies of natural melanin at different solution concentrations

The source of the optical properties of natural melanin persists as an impressive conundrum, hindering a thorough comprehension of the complicated photo-protective contribution of these extensive natural pigments and the pragmatic design of revolutionary bioinspired materials for optoelectronic functionalities. Melanin is a natural pigment distributed in vivo, and provides protection from the sun rays, exhibiting a strong wide-band UV–visible absorption. In the present study, we investigated the optical properties of natural melanin at different pH concentrations within the framework of experimental techniques, namely, UV–visible absorption, Fourier transform infrared spectroscopy (FTIR), and fluorescence spectroscopies. The results indicate that the optical absorption and fluorescence of natural melanin are enhanced within the near-UV and visible regimes with an increase in the solution concentration, are dependent on the pH level, and can impact the emergence of a broad band of visible absorption. The variations in the optical absorption spectra of natural melanin solutions at various pH levels will demonstrate novel rational strategies for controlling their optical properties for potential optoelectronic applications.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

Short communication: Surface charring from prescribed burning has minimal effects on soil bacterial community composition two weeks post-fire in jack pine barrens

Prescribed fire – the intentional use of fire to help achieve a land management goal – is becoming increasingly common as a land management practice. Soil physical, chemical, and biological properties can be affected by prescribed fires, but depend on the fire, soil type, residence time and frequency, and may not be changed substantially in low-severity burns. In this study, we examined soil bacterial community composition immediately post-fire (15 days) in a sandy jack pine barrens soil in Wisconsin, USA. Soil bacterial communities clustered significantly by sample site (p < 0.001) and by soil horizon (p = 0.048), but not by whether or not soil samples were visibly burned. There were also no significant differences in total relative abundance at the phylum level in visibly burned vs. not visibly burned soils, and only two significant differences in abundance or variability of individual taxa. Soil properties remained unchanged post-fire and the fire was visibly patchy, suggesting that the low severity prescribed fire most likely had a minimal soil heating effect. Furthermore, we suggest the minimal bacterial community composition shifts seen in this study were likely mediated more by plants than by direct heat-killing or changes to soil properties.

54 ENVIRONMENTAL SCIENCES↗