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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 1,225 records · Page 68
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

A Satellite Data-Driven, Client-Server Decision Support Application for Agricultural Water Resources Management

Water cycle extremes such as droughts and floods present a challenge for water managers and for policy makers responsible for the administration of water supplies in agricultural regions. In addition to the inherent uncertainties associated with forecasting extreme weather events, water planners need to anticipate water demands and water user behavior in a typical circumstances. This requires the use decision support systems capable of simulating agricultural water demand with the latest available data. Unfortunately, managers from local and regional agencies often use different datasets of variable quality, which complicates coordinated action. In previous work we have demonstrated novel methodologies to use satellite-based observational technologies, in conjunction with hydro-economic models and state of the art data assimilation methods, to enable robust regional assessment and prediction of drought impacts on agricultural production, water resources, and land allocation. These methods create an opportunity for new, cost-effective analysis tools to support policy and decision-making over large spatial extents. The methods can be driven with information from existing satellite-derived operational products, such as the Satellite Irrigation Management Support system (SIMS) operational over California, the Cropland Data Layer (CDL), and using a modified light-use efficiency algorithm to retrieve crop yield from the synergistic use of MODIS and Landsat imagery. Here we present an integration of this modeling framework in a client-server architecture based on the Hydra platform. Assimilation and processing of resource intensive remote sensing data, as well as hydrologic and other ancillary information occur on the server side. This information is processed and summarized as attributes in water demand nodes that are part of a vector description of the water distribution network. With this architecture, our decision support system becomes a light weight 'app' that connects to the server to retrieve the latest information regarding water demands, land use, yields and hydrologic information required to run different management scenarios. Furthermore, this architecture ensures all agencies and teams involved in water management use the same, up-to-date information in their simulations.

Agricultural↗
DOE OSTI2025

Controlling the Ru Island Decoration on Ni Nanoparticles to Tune the Activity for 5-Hydroxylmethylfurfural (HMF) Oxidation

Controlling the island decoration on metal nanoparticle supports is a major opportunity for improving the catalytic activity and an attractive synthetic challenge. The structure of the decorating metal determines how it interacts with the metal support and how it effectively catalyzes the reactants and the intermediates. In this work, we demonstrate that a slow-growth method maximizes the formation of Ru islands on faceted, branched Ni nanoparticles, thereby controlling the number of Ru–Ni atomic interactions and improving the catalytic activity. The Ru islands on branched Ni nanoparticles with the highest loading of Ru (9%) exhibited the highest activity for the electro-oxidation of biomass-derived 5-hydroxymethylfurfural (HMF). In conclusion, these results demonstrate the ability to synthetically control the second metal decoration to tune metal–support interactions, thereby enhancing the catalytic activity.

5-hydroxymethylfurfural↗
DOE OSTI2024

Influence of support on Rh-Co bimetallic catalysts for ethylene hydroformylation

Bimetallic Rh- and Co-based catalysts are promising materials for the heterogenous ethylene hydroformylation reaction. Here, in this study, the influence of a mesoporous silica (SBA-15) support on Rh and Co bimetallic interactions was investigated through a comparison with silica gel and alumina supports. The bimetallic catalyst supported on mesoporous silica (RhCo 3 /SBA-15) showed the best C 3 oxygenate yield among the three bimetallic catalysts. In-situ vibrational studies suggested moderate binding of the gem-dicarbonyl and Rh(CO)(C 2 H 4 ) intermediates due to this bimetallic interaction that led to improved hydroformylation performance. Kinetic studies revealed a lower hydroformylation barrier for the bimetallic compared to a Rh monometallic catalyst, and in-situ X-ray absorption spectroscopy investigations showed clear Rh-Co alloy formation on RhCo 3 /SBA-15. The bimetallic enhancement effect from the interaction with the mesoporous silica support shown here can be further optimized to design olefin hydroformylation catalysts.

58 GEOSCIENCES↗
NASA NTRS1981

Surface roughness effect on finite oil journal bearings

A theoretical study of the performance of finite oil journal bearings is made, considering the surface roughness effect. The total load supporting ability under such a condition derives from the hydrodynamic as well as asperity contact pressure. These two components of load are calculated separately. The average Reynolds equation for partially lubricated surfaces is used to evaluate hydrodynamic pressure. An analytical expression for average film thickness is obtained and introduced to modify the average Reynolds equation. The resulting differential equation is then solved numerically by finite difference methods for mean hydrodynamic pressure, which in turn gives the hydrodynamic load. Assuming the surface height distribution as Gaussian, the asperity contact pressure is found. The effect of surface roughness parameter, surface pattern, eccentricity ratio, and length to diameter ratio on hydrodynamic load and on side leakage is investigated. It is shown that hydrodynamic load increases with increasing surface roughness when both journal and bearing surfaces have identical roughness structures or when the journal only has a rough surface. The trend of hydrodynamic load is reversed if the journal surface is smooth and the bearing surface is rough.

Majumdar, B. C.↗
DOE OSTI2018

Direct Conversion of Methane to Methanol on Ni-Ceria Surfaces: Metal-Support Interactions and Water-enabled Catalytic Conversion by Site Blocking

The transformation of methane into methanol or higher alcohols at moderate temperature and pressure conditions is of great environmental interest and remains a challenge despite many efforts. Extended surfaces of metallic nickel are inactive for a direct CH 4 → CH 3 OH conversion. This experimental and computational study provides clear evidence that low Ni loadings on a CeO 2 (111) support can perform a direct catalytic cycle for the generation of methanol at low temperature using oxygen and water as reactants, with a higher selectivity than ever reported for ceria-based catalysts. On the basis of ambient pressure X-ray photoemission spectroscopy and density functional theory calculations, we demonstrate that water plays a crucial role in blocking catalyst sites where methyl species could fully decompose, an essential factor for diminishing the production of CO and CO 2 , and in generating sites on which methoxy species and ultimately methanol can form. In addition to water-site blocking, one needs the effects of metal-support interactions to bind and activate methane and water. Lastly, these findings should be considered when designing metal/oxide catalysts for converting methane to value-added chemicals and fuels.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Enhancing Activity and Reducing Cost for Electrochemical Reduction of CO 2 by Supporting Palladium on Metal Carbides

Electrochemical CO 2 reduction reaction (CO 2 RR) with renewable electricity is a potentially sustainable method to reduce CO 2 emissions. Palladium supported on cost-effective transition-metal carbides (TMCs) are studied to reduce the Pd usage and tune the activity and selectivity of the CO 2 RR to produce synthesis gas, using a combined approach of studying thin films and practical powder catalysts, in situ characterization, and density functional theory (DFT) calculations. Notably, Pd/TaC exhibits higher CO 2 RR activity, stability and CO Faradaic efficiency than those of commercial Pd/C while significantly reducing the Pd loading. In situ measurements confirm the transformation of Pd into hydride (PdH) under the CO 2 RR environment. DFT calculations reveal that the TMC substrates modify the binding energies of key intermediates on supported PdH. As a result, this work suggests the prospect of using TMCs as low-cost and stable substrates to support and modify Pd for enhanced CO 2 RR activity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Glass production rate in electric furnaces for radioactive waste vitrification

Correlating the melting rates of feeds in electric melters with results of simple laboratory experiments can help evaluate melter feed additives and their effects on melting rate, and support the feed scheduling and plant operation. A recently proposed melting rate correlation (MRC) equation, relating the melting rate to melt viscosity, feed-to-glass conversion heat, and cold-cap bottom temperature, was tested using data from experiments covering various feed compositions and melter operating parameters. The MRC equation is shown to reasonably represent the measured data and thus can be used to quantify how individual variables (melt viscosity, cold-cap bottom temperature, conversion heat, melter operating temperature, and bubbling rate) affect the glass production rate.

Lee, Seung Min↗
NASA NTRSDate not supplied

Dust Solution Testing Initiative (DuSTI): Infusing Commercial Off the Shelf Dust Mitigation Technologies with NASA Practices

Dust is one of the most significant hazards to human lunar exploration. However, since the Apollo program concluded, limited research has been performed on lunar dust mitigation technologies. The safety of the crew members and sustainability of habitats, science, and supporting hardware depend on effective dust mitigation techniques and technologies. As NASA pursues a new generation of lunar missions with the Artemis program, the project team will pursue dust mitigation solutions with the Dust Solution Testing Initiative (DuSTI). DuSTI is a lunar dust mitigation effort that involves performing tests on commercial off the shelf (COTS) technologies over FY21. DuSTI will preform component and subsystem tests in dusty environments for up to five technologies with high potential. The specific technologies identified for study were selected based on several factors, including a market analysis of current terrestrial dust mitigation applications, availability of the technology, accessibility of various testing facilities, and cost of procurement. These technologies support the active and passive dust mitigation requirements of filtration systems, electro-mechanical systems, electro-static systems, surface coatings, textiles, and silicone polymers. Technology Readiness Level (TRL) will be increased by validating components in relevant environments. For example, if the COTS technology is at a TRL 9 for terrestrial use but at a 4-5 TRL for use in the lunar environment, we will test that technology in a lunar dust environment to increase the TRL for use on the Moon.

lunar dust↗
DOE OSTI2018

In-situ Characterization of Cu/CeO 2 Nanocatalysts during CO 2 Hydrogenation: Morphological Effects of Nanostructured Ceria on the Catalytic Activity

Here, a combination of time-resolved X-ray diffraction (TR-XRD), ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to carry out an in-situ characterization of Cu/CeO 2 nanocatalysts during the hydrogenation of CO 2 . Morphological effects of the ceria supports on the catalytic performances were investigated by examining the behavior of copper/ceria-nanorods (NR) and nanospheres (NS). At atmospheric pressures, the hydrogenation of CO 2 on the copper-ceria catalysts produced mainly CO through the reverse-water gas shift reaction (RWGS) and a negligible amount of methanol. The Cu/CeO 2 -NR catalyst displayed the higher activity, which demonstrates that the RWGS is a structure sensitive reaction. In-situ TR-XRD and AP-XPS characterization showed significant changes in the chemical state of the catalysts under reaction conditions with the copper being fully reduced and a partial Ce 4+ to Ce 3+ transformation occurring. A more effective CO 2 dissociative activation at high temperature and a preferential formation of active bidentate carbonate and formate intermediates over CeO 2 (110) terminations are probably the main reasons for the better performance of the Cu/CeO 2 -NR catalyst in the RWGS reaction.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Study of Ga incorporation in glassy arsenic selenides by high-resolution XPS and EXAFS

Effect of Ga addition on the structure of vitreous As{sub 2}Se{sub 3} is studied using high-resolution X-ray photoelectron spectroscopy and extended X-ray absorption fine structure techniques. The “8-N” rule is shown to be violated for Ga atoms and, possibly, for certain number of As atoms. On the contrary, Se keeps its 2-fold coordination according to “8-N” rule in the amorphous phase throughout all the compositions. Crystalline inclusions appear in the amorphous structure of the investigated glasses at Ga concentrations greater than 3 at. %. These inclusions are presumably associated with Ga{sub 2}Se{sub 3} crystallites and transition phases/defects formed at the boundaries of these crystallites and host amorphous matrix. The existence of Ga–As and Se–Se bonds in the samples with higher Ga content is supported by present studies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Experimental and theoretical investigation of the first-order hyperpolarizability of a class of triarylamine derivatives

This paper reports on the static and dynamic first-order hyperpolarizabilities of a class of push-pull octupolar triarylamine derivatives dissolved in toluene. We have combined hyper-Rayleigh scattering experiment and the coupled perturbed Hartree-Fock method implemented at the Density Functional Theory (DFT) level of theory to determine the static and dynamic (at 1064 nm) first-order hyperpolarizability (β{sub HRS}) of nine triarylamine derivatives with distinct electron-withdrawing groups. In four of these derivatives, an azoaromatic unit is inserted and a pronounceable increase of the first-order hyperpolarizability is reported. Based on the theoretical results, the dipolar/octupolar character of the derivatives is determined. By using a polarizable continuum model in combination with the DFT calculations, it was found that although solvated in an aprotic and low dielectric constant solvent, due to solvent-induced polarization and the frequency dispersion effect, the environment substantially affects the first-order hyperpolarizability of all derivatives investigated. This statement is supported due to the solvent effects to be essential for the better agreement between theoretical results and experimental data concerning the dynamic first-order hyperpolarizability of the derivatives. The first-order hyperpolarizability of the derivatives was also modeled using the two- and three-level models, where the relationship between static and dynamic first hyperpolarizabilities is given by a frequency dispersion model. Using this approach, it was verified that the dynamic first hyperpolarizability of the derivatives is satisfactorily reproduced by the two-level model and that, in the case of the derivatives with an azoaromatic unit, the use of a damped few-level model is essential for, considering also the molecular size of such derivatives, a good quantitative agreement between theoretical results and experimental data to be observed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Facile morphology controllable synthesis of PtPd nanorods on graphene-multiwalled carbon nanotube hybrid support as efficient electrocatalysts for oxygen reduction reaction

Highlights: • G–M hybrid was prepared by a novel modified Hummers method followed by thermal annealing. • G–M was verified to be more efficient as the electrocatalyst support compared with G. • Ultrathin PtPd alloy nanorods were supported on the G–M hybrid. • The electrochemical activity of PtPd NRs/G–M outperforms the commercial Pt/C. - Abstract: One-dimensional (1D) anisotropic platinum-based nanorods are particularly attractive electrocatalysts for oxygen reduction reaction (ORR) owing to the inherent structural advantages. In this work, we report the growth of ultrathin PtPd alloy nanorods (3–4 nm) on Graphene-Multiwalled carbon nanotube (G–M) hybrid support via a facile surfactant-free and template-free method as the efficient electrocatalyst for ORR. The as-synthesized PtPd NRs/G–M catalyst exhibits more excellent activity and better durability toward ORR than Pt NRs/G and Pt NRs/G–M catalysts. Noteworthily, it shows an outstanding half-wave potential of 0.810 V and mass activity of 49.5 mA mg{sup –1} at 0.85 V, which are 30 mV and 2.1 times higher than those of commercial 40 wt% Pt/C (JM40) catalyst, respectively. After the accelerated durability tests (ADTs), it also maintains superior stability than JM40. The superior performance is attributed to the combination of the advantageous 1D morphological motif and the synergistic effect with G–M support.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2021

Magnetoelastic coupling and spin contributions to entropy and thermal transport in biferroic yttrium orthochromite

Direct engineering of material properties through exploitation of spin, phonon, and charge-coupled degrees of freedom is an active area of development in materials science. However, the relative contribution of the competing orders to controlling the desired behavior is challenging to decipher. In particular, the independent role of phonons, magnons, and electrons, quasiparticle coupling, and relative contributions to the phase transition free energy largely remain unexplored, especially for magnetic phase transitions. Here, we study the lattice and magnetic dynamics of biferroic yttrium orthochromite using Raman, infrared, and inelastic neutron spectroscopy techniques, supporting our experimental results with first-principles lattice dynamics and spin-wave simulations across the antiferromagnetic transition at T N ~ 138 K. Spectroscopy data and simulations together with the heat capacity (C p ) measurements, allow us to quantify individual entropic contributions from phonons (0.01 ± 0.01k B atom -1 ), dilational (0.03 ± 0.01k B atom -1 ), and magnons (0.11 ± 0.01k B atom -1 ) across TN. High-resolution phonon measurements conducted in a magnetic field show that anomalous T-dependence of phonon energies across TN originates from magnetoelastic coupling. Additionally, phonon scattering is primarily governed by the phonon–phonon coupling, with little contribution from magnon–phonon coupling, short-range spin correlations, or magnetostriction effects; a conclusion further supported by our thermal conductivity measurements conducted up to 14 T, and phenomenological modeling.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

Multitasking mesoporous nanomaterials for biorefinery applications

Mesoporous silica nanoparticles (MSNs) have attracted great interest for last two decades due to their unique and advantageous structural properties, such as high surface area, pore volume, stable mesostructure, tunable pore size and controllable particle morphology. The robust silica framework provides sites for organic modifications, making MSNs ideal platforms for adsorbents and supported organocatalysts. In addition, the pores of MSNs provide cavities/ channels for incorporation of metal and metal oxide nanoparticle catalysts. These supported metal nanoparticle catalysts benefit from confined local environments to enhance their activity and selectivity for various reactions. Biomass is considered as a sustainable feedstock with potential to replace diminishing fossil fuels for the production of biofuels. Among several strategies, one of the promising methods of biofuel production from biomass is to reduce the oxygen content of the feedstock in order to improve the energy density. This can be achieved by creating C-C bonds between biomass derived intermediates to increase the molecular weight of the final hydrocarbon molecules. In this context, pore size and organic functionality of MSNs are varied to obtain the ideal catalyst for a C-C bond forming reaction: the aldol condensation. The mechanistic aspects of this reaction in supported heterogeneous catalysts are explored. The modification of supported organocatalyst and the effect of solvent on the reaction are rationalized. The significance of two functional surfaces of MSNs is exploited by enzyme immobilization on the external surface and organo catalyst functionalization on the internal surface. Using this bifunctional catalyst, the tandem conversion of small chain alcohols into longer chain hydrocarbon molecules is demonstrated. The ability to incorporate metal and metal oxide nanoparticles in the pores and subsequent functionalization led to develop organic modified magnetic MSNs (OM-MSNs) for applications in microalgae biorefinery. Two different integrated biorefinery systems are highlighted. (i) OM-MSNs are used to harvest microalgae and selectively sequester free fatty acids (FFAs). (ii) OM-MSNs are shown to selectively sequester FFAs and convert them into diesel-range liquid hydrocarbon fuels. A similar MSN supported metal nanoparticle catalyst is demonstrated to transform FFAs into green diesel with even greater activity and selectivity. The incorporation of a different organic functional group into MSN provides a selective adsorbent for separation and purification of α-tocopherol from microalgae oil. The functional group with electron deficient aromatic rings demonstrated high sequestration capacity and selectivity of {alpha}-tocopherol.

09 BIOMASS FUELS↗
DOE OSTI2023

Tropical Tree Crop Simulation with a Process-Based, Daily Timestep Simulation Model (ALMANAC): Description of Model Adaptation and Examples with Coffee and Cocoa Simulations

Coffee (Coffea species) and Cocoa (Theobroma cacao) are important cash crops grown in the tropics but traded globally. This study was conducted to apply the ALMANAC model to these crops for the first time, and to test its ability to simulate them under agroforestry management schemes and varying precipitation amounts. To create this simulation, coffee was grown on a site in Kaua’i, Hawai’i, USA, and cocoa was grown on a site in Sefwi Bekwai, Ghana. A stand-in for a tropical overstory tree was created for agroforestry simulations using altered parameters for carob, a common taller tropical tree for these regions. For both crops, ALMANAC was able to realistically simulate yields when compared to the collected total yield data. On Kaua’i, the mean simulated yield was 2% different from the mean measured yield, and in all three years, the simulated values were within 10% of the measured values. For cocoa, the mean simulated yield was 3% different from the mean measured yield and the simulated yield was within 10% of measured yields for all four available years. When precipitation patterns were altered, in Ghana, the wetter site showed lower percent changes in yield than the drier site in Hawai’i. When agroforestry-style management was simulated, a low Leaf Area Index (LAI) of the overstory showed positive or no effect on yields, but when LAI climbed too high, the simulation was able to show the detrimental effect this competition had on crop yields. These simulation results are supported by other literature documenting the effects of agroforestry on tropical crops. This research has applied ALMANAC to new crops and demonstrated its simulation of different management and environmental conditions. The results show promise for ALMANAC’s applicability to these scenarios as well as its potential to be further tested and utilized in new circumstances.

60 APPLIED LIFE SCIENCES↗
NASA NTRS1995

Influence of backup bearings and support structure dynamics on the behavior of rotors with active supports

This semiannual status report lists specific accomplishments made on the research of the influence of backup bearings and support structure dynamics on the behavior of rotors with active supports. Papers have been presented representing work done on the T-501 engine model; an experimental/simulation study of auxiliary bearing rotordynamics; and a description of a rotordynamical model for a magnetic bearing supported rotor system, including auxiliary bearing effects. A finite element model for a foil bearing has been developed. Additional studies of rotor/bearing/housing dynamics are currently being performed as are studies of the effects of sideloading on auxiliary bearing rotordynamics using the magnetic bearing supported rotor model.

Flowers, George T.↗
DOE OSTI2021

Convergent Hydraulic Redistribution and Groundwater Access Supported Facilitative Dependency Between Trees and Grasses in a Semi‐Arid Environment

Abstract Hydraulic redistribution is the transport of water from wet to dry soil layers, upward or downward, through plant roots. Often in savanna and woodland ecosystems, deep‐rooted trees, and shallow‐rooted grasses coexist. The degree to which these different species compete for or share soil‐water derived from precipitation or groundwater, as well as how these interactions are altered by hydraulic redistribution, is unknown. We use a multilayer canopy model and field observations to examine how the presence of deep, but tree‐root accessible, groundwater impacts seasonal patterns of hydraulic redistribution, and interaction between coexisting vegetation species in a semiarid riparian woodland (US‐CMW). Based on the simulation, trees absorb moisture at the water table (∼10 m depth) and release it in the shallow soil depth (0–3 m) during the dry pre‐monsoon season. We observed the occurrence of a new convergent hydraulic redistribution pattern during the monsoon season, where moisture is transported from both the near‐surface (0–0.5 m) and the water table to intermediate soil layers (1–5 m) through tree roots. We found that hydraulic redistribution demonstrates a growth facilitation effect at this site, supporting 49% of growing season tree transpiration and 14% of the grass transpiration. Compared to a similarly structured upland savanna without accessible groundwater, the riparian site shows an increased amount of hydraulically redistributed water and more facilitative water use between coexisting grasses and trees. These results shed light on the linkage between accessible groundwater and the role of hydraulic redistribution on the interaction between deep‐rooted and shallow‐rooted vegetation.

Lee, E.↗