SEARCH · Search NASA

Results for “Delta”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8

All sources NASA NTRS DOE OSTI

NASA NTRS2017

Stratigraphy and Evolution of Delta Channel Deposits, Jezero Crater, Mars

The Jezero impact crater hosted an open-basin lake that was active during the valley network forming era on early Mars. This basin contains a well exposed delta deposit at the mouth of the western inlet valley. The fluvial stratigraphy of this deposit provides a record of the channels that built the delta over time. Here we describe observations of the stratigraphy of the channel deposits of the Jezero western delta to help reconstruct its evolution.

sedimentology↗

NASA NTRSDate not supplied

NASA Delta Airlines Technical Interchange Meeting

The Digital Information Sub-project will hold a Technical Interchange Meeting (TIM) with Delta Airlines to discuss potential collaboration opportunities as well as discuss upcoming NASA-led demonstrations. This interchange meeting will solicit feedback from Delta for consideration of the sub-project in upcoming development and to encourage future participation and collaboration. Additionally, Delta will provide insight into airline operations to allow NASA to learn more about airline operations.

Digital Information Platform↗

DOE OSTI2025

Temporal Patterns in Soil Redox Potential Vary Across a Freshwater Coastal Delta

Widespread and persistent flooding is submerging coastal ecosystems, particularly along the Louisiana Gulf coast, where flooding results from the compounding effects of ground subsidence and rising sea level. Restoration projects aim to mitigate land loss by diverting sediment loads from rivers into degraded areas to increase ground elevation. To predict how coastal ecosystems will change over time in response to projected changes in relative sea level and restoration, it is necessary to understand how subsurface biogeochemical processes respond to dynamic hydrologic forcings. Here, this study evaluates how environmental parameters that integrate biogeochemical processes vary with water table fluctuations in the freshwater Wax Lake Delta (WLD) in Louisiana, USA, where water diversions have formed one of the only active deltas along the coast. High‐frequency observations of water level, soil redox potential, specific conductance and pH were made for 1 year along elevation transects located on the older, proximal and younger, distal ends of a deltaic island. Redox responded rapidly to changing water tables, with fluctuations occurring primarily in shallow soils (< 20 cm) and at higher elevations. Deeper soils and those at lower elevation remained inundated and reduced. Semi‐diurnal tidal fluctuations were pronounced in younger, distal soils, presumably due to rapid groundwater exchange with the river channel. Tidal signals were muted in older soils that instead exhibited seasonal variability associated with river discharge and evapotranspiration. Although much of the delta sediments are persistently reducing and anoxic, redox fluctuations in the natural levees that border the deltaic islands likely drive high rates of biogeochemical activity. Evaluating how hydrology drives the frequency and duration of redox fluctuations provides a basis for understanding how biogeochemical processes might vary with complex hydrological interactions in coastal systems.

Herndon, Elizabeth [Oak Ridge National Laboratory ↗

DOE OSTI2024

AmeriFlux FLUXNET-1F US-YK2 Yukon-Kuskokwim Delta, Izaviknek-Kingaglia uplands, Unburned

This is the AmeriFlux Management Project (AMP) created FLUXNET-1F version of the carbon flux data for the site US-YK2 Yukon-Kuskokwim Delta, Izaviknek-Kingaglia uplands, Unburned. This is the FLUXNET version of the carbon flux data for the site US-YK2 Yukon-Kuskokwim Delta, Izaviknek-Kingaglia uplands, Unburned produced by applying the standard ONEFlux (1F) software. Site Description - Tower installed in the Yukon-Kuskokwin Delta in September 2019. Discontinuos permafrost zone in a wetland tundra ecosystem characterized by peat plateaus and wetlands.

Natali, Sue↗

DOE OSTI2025

AmeriFlux FLUXNET-1F CA-DSM Delta Salt Marsh

This is the AmeriFlux Management Project (AMP) created FLUXNET-1F version of the carbon flux data for the site CA-DSM Delta Salt Marsh. This is the FLUXNET version of the carbon flux data for the site CA-DSM Delta Salt Marsh produced by applying the standard ONEFlux (1F) software. Site Description - This site is a tidal salt marsh on the eastern side of the Boundary Bay Wildlife Management Area (WMA) in Delta, British Columbia, Canada. This area is located on the southern front of the Fraser River. The total area of the Boundary Bay WMA is 11,470 ha, and the eastern part surrounding the flux tower accounts for 39 ha. This area is surrounded by farms and dikes. The Provincial Government purchased this area in 1974 limiting public access and designated it as WMA in 1995. This area has a mixed semidiurnal tidal cycle. The dominant species is Saltgrass (Distichlis spicata) with a canopy height of ~40 cm. The tower is in a high marsh system and was installed to analyze energy, H2O, CO2, and CH4 fluxes on September 3, 2021.

Knox, Sara [The University of British Columbia]↗

DOE OSTI2026

AmeriFlux FLUXNET-1F US-YK1 Yukon-Kuskokwim Delta, Izaviknek-Kingaglia uplands, Burned 2015

This is the AmeriFlux Management Project (AMP) created FLUXNET-1F version of the carbon flux data for the site US-YK1 Yukon-Kuskokwim Delta, Izaviknek-Kingaglia uplands, Burned 2015. This is the FLUXNET version of the carbon flux data for the site US-YK1 Yukon-Kuskokwim Delta, Izaviknek-Kingaglia uplands, Burned 2015 produced by applying the standard ONEFlux (1F) software. Site Description - Tower installed in the Yukon-Kuskokwim Delta in July 2019, in an area that was burned in year 2015. Discontinuous permafrost zone in a wetland tundra ecosystem characterized by peat plateaus and wetlands

Natali, Susan [Woodwell Climate Research Center]↗

DOE OSTI2024

Delta-Rice: A HDF5 Compression Plugin optimized for Digitized Detector Data

Delta-Rice is an HDF5 (The HDF Group et al., 2020) filter plugin that was developed to compress digitized detector signals recorded by the Nab experiment (Fry et al., 2019), a fundamental neutron physics experiment. This is a two-step process where incoming data is passed through a pre-processing filter and then compressed with Rice coding. A routine for determining the optimal pre-processing filter for a dataset is provided along with an example GPU deployment. When applied to data collected by the Nab data acquisition system, this method produced output files 29% their initial size, and was able to do so with an average read/write throughput in excess of 2 GB/s on a single CPU. Compared to the widely used Gzip compression routine, Delta-Rice reduces the file size by 33% more with over an order of magnitude increase in read/write throughput. Delta-Rice is available on CPU to users through the HDF5 library.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2024

Progress Towards an Expanded Search for Neutral-Current Delta Radiative Decays in MicroBooNE

In this note, we present progress toward an expanded search for neutral current Delta radiative decays (NC $\Delta \rightarrow N\gamma$) in MicroBooNE. We present sensitivities for several tests of the MiniBooNE Low Energy Excess (LEE) under NC $\Delta \rightarrow N\gamma$ scaling hypotheses, with significantly enhanced sensitivity relative to previous tests. These selections can also be used for additional single photon searches in the future, including searches which target more specific hadronic final states and particular regions of shower kinematic phase space.

43 PARTICLE ACCELERATORS↗

NASA NTRS1972

Application of the leading edge suction analogy to prediction of longitudinal load distribution and pitching moments for sharp edged delta wings

The leading-edge-suction analogy of Polhamus has been used to develop the longitudinal load distribution of the vortex lift for delta wings. This distribution is shown to be similar in shape to that of the potential-flow longitudinal loading for delta wings having aspect ratios of 2 or less. The totals of the two theoretical distributions for delta wings with an aspect ratio near 1 are in good agreement with the experimentally determined loadings over the angle-of-attack range from 0 to 30 deg. The corresponding predicted pitching moments show slightly more stability than those measured, because of loss of lift near the wing tips.

Snyder, M. H., Jr.↗

NASA NTRS1973

Observations of the plant growth and annual flooding in the inland delta of the Niger River, west Africa

The author has identified the following significant results. A large potential irrigation area with water delivery system in place was identified from ERTS-1 imagery. The site is in the Sahara Desert. Color additive change detection imagery was used to assess ground water potentials in the Savannah in conjunction with a major US AID-Mali livestock sector initiative. The potential capacity to map laterite deposits in the Inland Delta from space was established with the help of aerial and ground surveys. A color composite of the Inland Delta could have saved French biogeographers 3 5/6 man-years of professional field work had it been available, according to the man who prepared a plant community map of part of the southern Inland Delta.

Macleod, N. H.↗

NASA NTRS1975

Quaternary and quinary modifications of eutectic superalloys strengthened by delta Ni3Cb lamellae and gamma prime Ni3Al precipitates

By means of a compositional and heat treatment optimization program based on the quaternary gamma/gamma prime-delta, a tantalum modified gamma/gamma prime-delta alloy with improved shear and creep strength combined with better cyclic oxidation resistance was identified. Quinary additions, quaternary adjustments, and heat treatment were investigated. The tantalum modified gamma/gamma prime-delta alloy possessed a slightly higher liquidus temperature and exhibited rupture strength exceeding NASA VIA by approximately three and one-half Larson-Miller parameters (C = 20) above 1000 C. Although improvements in longitudinal mechanical properties were achieved, the shear and transverse strength property goals of the program were not met and present a continuing challenge to the alloy metallurgist.

Lemkey, F. D.↗

NASA NTRS1975

Effect of thermal cycling in a Mach 0.3 burner rig on properties and structure of directionally solidified gamma/gamma prime - delta eutectic

Tensile and stress rupture properties at 1040 C of a thermally cycled gamma/gamma prime - delta eutectic were essentially equivalent to the as-grown properties. Tensile strength and rupture life at 760 C appeared to decrease slightly by thermal cycling. Thermal cycling resulted in gamma prime coarsening and Widmanstatten delta precipitation in the gamma phase. An unidentified precipitate, presumably gamma prime, was observed within the delta phase. The eutectic alloy exhibited a high rate of oxidation-erosion weight loss during thermal cycling in the Mach 0.3 burner rig.

Gray, H. R.↗

NASA NTRS1975

Scattering of 4.5 eV electrons by ground /x 3 Sigma g minus/ state and metastable /a 1 Delta g/ oxygen molecules

The paper reports on differential and integral cross sections for scattering of 4.5 eV electrons by ground state (x 3 Sigma g minus) and metastable (a 1 Delta g) oxygen molecules in the -2.0 eV to plus 2.0 eV energy loss range. The cross section for the (a 1 Delta g to b 1 Sigma g plus) transition was found to be more than an order of magnitude larger than that of the excitation of the b state from the ground state. It was found that the principle of detailed balance can be applied to the rotationally unresolved inelastic and superelastic electronic transitions between the (x 3 Sigma g minus) and (a 1 Delta g) states, which indicates that for this transition one may neglect the very different rotational level structure of the two states in estimating superelastic cross section from inelastic data to an accuracy of about 15 per cent.

Hall, R. I.↗

NASA NTRS1975

Use of LANDSAT data for resources investigation in the lower basin of Danube and Danube Delta

The author has identified the following significant results. A most important is that bands 4 and 5 very clearly show the sedimentary discharge into the sea and the spreading regime in the sea at the mouth of the Danube and out at sea at great distances to over 100 km. Another particularly significant result is shown by bands 6 and 7, presenting the successive stages of sediments in the Danube Delta, with the clear marking of the separation between the fluvial and marine delta. The survey of floods and of some of their effects may also be studied on all of the bands in the complex area of the Danube Delta and in the lower basin of the Danube.

Oprescu, N.↗

NASA NTRS1976

Effect of thermal cycling in a Mach 0.3 burner rig on properties and structure of directionally solidified gamma/gamma prime-delta eutectic

An experimental study was carried out to evaluate the effect of cyclic thermal exposures on the mechanical properties of a gamma/gamma prime-delta eutectic alloy parallel to the growth direction. The alloy had a nominal composition by weight of Ni-20 Nb-6 Cr-2.5 Al and was directionally solidified at 3 cm/hr in a furnace with a thermal gradient of at least 200 C/cm. Bars of the alloy were exposed in a Mach 0.3 burner rig and cycled 300 times between 1100 and 425 C. Oxidation-erosion characteristics of the alloy were determined by weight loss measurements at 300-cycle intervals. After cyclic exposure, stress rupture and tensile tests were performed at both 760 and 1040 C. Microstructural changes from cyclic exposure were determined. Thermal cycling resulted in gamma prime coarsening and Widmanstaetten delta precipitation in the gamma phase. An unidentified precipitate, presumably gamma prime, was observed within the delta phase. These microstructural changes did not affect the mechanical properties of the eutectic. High oxidation-erosion weight loss rate was observed.

Gray, H. R.↗

NASA NTRS1977

The effect of delta T /oxidizing temperature minus cooling temperature/ on oxide spallation

Several alloys (one iron base and five nickel base) were cyclically oxidized in a series of tests in which the higher temperature (1100 or 1200 C) of the cycle was fixed at a level to allow ample oxidation in reasonable time and the lower temperature was variable to allow cycle temperature differences of up to 1400 C. For all nickel alloys, as delta T increased the extent of spallation increased. This effect was attributed to thermal expansion mismatches between the oxide and the nickel substrate. The FeCrAl alloy was not sensitive to delta T and resisted spalling at delta T levels to 1400 C. FeCrAl, and the Al2O3 scale which forms on it, have thermal expansion coefficients which are substantially more alike than any of the other oxide-metal combinations tested.

Deadmore, D. L.↗

NASA NTRS1978

Feasibility study of tungsten as a diffusion barrier between nickel-chromium-aluminum and Gamma/Gamma prime - Delta eutectic alloys

Coating systems proposed for potential use on eutectic alloy components in high-temperature gas turbine engines were studied with emphasis on deterioration of such systems by diffusion. A 1-mil thick W sheet was placed between eutectic alloys and a NiCrAl layer. Layered test specimens were aged at 1100 C for as long as long as 500 hours. Without the W barrier, the delta phase of the eutectic deteriorated by diffusion of Nb into the NiCrAl. Insertion of the W barrier stopped the diffusion of Nb from delta. Chromium diffusion from the NiCrAl into the gamma/gamma prime phase of the eutectic was greatly reduced by the barrier. However, the barrier thickness decreased with time; and W diffused into both the NiCrAl and the eutectic. When the delta platelets were alined parallel to the NiCrAl layer, rather than perpendicular, diffusion into the eutectic was reduced.

Young, S. G.↗

NASA NTRS1978

Voice encoding for the Space Shuttle using adaptive delta modulation

The paper describes the SONG and modified ABATE adaptive delta modulation algorithms for voice encoding. Waveforms of the response of the delta modulators to channel errors are given, and performance data which show the relationship between channel errors and word intelligibility are provided. An analytic derivation yielding a comparison between PCM and adaptive delta modulation with respect to channel errors is given. The Space Shuttle is employing the modified-ABATE device because it can tolerate a high error rate and operates at a relatively low sampling rate.

Schilling, D. L.↗