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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 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

High efficiency radio frequency antennas for amplifier free quantum sensing applications

Radio frequency (RF) signals are frequently used in emerging quantum applications due to their spin state manipulation capability. Efficient coupling of RF signals into a particular quantum system requires the utilization of carefully designed and fabricated antennas. Nitrogen vacancy (NV) defects in diamond are commonly utilized platforms in quantum sensing experiments with the optically detected magnetic resonance (ODMR) method, where an RF antenna is an essential element. We report on the design and fabrication of high efficiency coplanar RF antennas for quantum sensing applications. Single and double ring coplanar RF antennas were designed with -37 dB experimental return loss at 2.87 GHz, the zero-field splitting frequency of the negatively charged NV defect in diamond. The efficiency of both antennas was demonstrated in magnetic field sensing experiments with NV color centers in diamond. In conclusion, an RF amplifier was not needed, and the 0 dB output of a standard RF signal generator was adequate to run the ODMR experiments due to the high efficiency of the RF antennas.

47 OTHER INSTRUMENTATION↗
NASA NTRS2022

Hybrid Kinetic Model of the Interaction Between the Dense Plasma Clouds and Magnetospheric Plasma on Large Time and Spatial Scales, and Comparison With MMS Observations

We present a new simulation results of the cloud dynamics in the ambient magnetospheric plasma on the large time and spatial scales. It was assumed that these impulsive structures observed by the MMS spacecraft originally were created because of the reconnection at the magnetopause. Our new 3-D hybrid kinetic modeling on the large time and spatial scales captures several of these processes: an excitation of the electromagnetic waves (whistler and shear-Alfvén waves) and plasma instabilities (mirror and flute); a formation of shock waves, and collapsing diamagnetic cavity; particle acceleration. A strong overshoot in plasma density profile was observed in the modeling and MMS observation at the interface between the cloud and magnetospheric plasma. The cloud expansion into ambient magnetospheric plasma causes the flute waves connected with excitation of the Rayleigh-Taylor instability observed at the overshoot in plasma density profile across the external magnetic field. The modeling demonstrates a formation of the whistler waves at the initial stage which propagate in the external magnetic field direction. At the later stage, a formation of shear-Alfvén waves was observed

A. S. Lipatov↗
NASA NTRS1974

High latitude ionospheric winds related to solar-interplanetary conditions

Two recent results imply that the distribution of winds in the polar ionosphere should change as a function of the direction of the interplanetary magnetic field. From the motions of chemically released ion and neutral clouds, it is apparent that neutral winds in the high latitude ionosphere are driven principally by ion drag forces. OGO-6 electric field measurements have demonstrated that there are definite relationships between the time latitude distribution of ionospheric plasma convection and interplanetary magnetic field parameters, and also that the distribution is most sensitive to the azimuthal angle of the interplanetary field. The lower altitude, meteorological effects of these externally driven ionospheric winds are not known. However, observations of infrasonic waves following sudden ionization enhancements indicate the existence of momentum transfer.

Heppner, J. P.↗
NASA NTRS1973

High latitude ionospheric winds related to solar-interplanetary conditions

Treated jointly, two recent results imply that the distribution of winds in the polar ionosphere should change as a function of the direction of the interplanetary magnetic field. (1) From the motions of chemically released ion and neutral clouds, it is apparent that neutral winds in the high latitude ionosphere are driven principally by ion drag forces. (2) OGO-6 electric field measurements have demonstrated that there are definite relationships between the time-latitude distribution of ionospheric plasma convection and interplanetary magnetic field parameters, and also that the distribution is most sensitive to the azimuthal angle of the interplanetary field. Although direct neutral wind to interplanetary magnetic field comparisons are not available, logic clearly implies a close relationship. The lower altitude, meteorological effects of these externally driven ionospheric winds are not known. However, observations of infrasonic waves following sudden ionization enhancements indicate the existence of momentum transfer.

Heppner, J. P.↗
DOE OSTI2022

Parked aeroelastic field rotor response for a 20% scaled demonstrator of a 13‐MW downwind turbine

Abstract Aeroelastic parked testing of a unique downwind two‐bladed subscale rotor was completed to characterize the response of an extreme‐scale 13‐MW turbine in high‐wind parked conditions. A 20% geometric scaling was used resulting in scaled 20‐m‐long blades, whose structural and stiffness properties were designed using aeroelastic scaling to replicate the nondimensional structural aeroelastic deflections and dynamics that would occur for a lightweight, downwind 13‐MW rotor. The subscale rotor was mounted and field tested on the two‐bladed Controls Advanced Research Turbine (CART2) at the National Renewable Energy Laboratory's Flatiron Campus (NREL FC). The parked testing of these highly flexible blades included both pitch‐to‐run and pitch‐to‐feather configurations with the blades in the horizontal braked orientation. The collected experimental data includes the unsteady flapwise root bending moments and tip deflections as a function of inflow wind conditions. The bending moments are based on strain gauges located in the root section, whereas the tip deflections are captured by a video camera on the hub of the turbine pointed toward the tip of the blade. The experimental results are compared against computational predictions generated by FAST, a wind turbine simulation software, for the subscale and full‐scale models with consistent unsteady wind fields. FAST reasonably predicted the bending moments and deflections of the experimental data in terms of both the mean and standard deviations. These results demonstrate the efficacy of the first such aeroelastically scaled turbine test and demonstrate that a highly flexible lightweight downwind coned rotor can be designed to withstand extreme loads in parked conditions.

17 WIND ENERGY↗
DOE OSTI2020

Influence of physical and chemical hydrology on bioremediation of a U-contaminated aquifer informed by reactive transport modeling incorporating 238 U/ 235 U ratios

Microbially-catalyzed reductive immobilization of aqueous uranium (U) as a solid phase has been proposed as a U remediation technique. Both laboratory and field experiments have demonstrated that this reduction reaction alters the 238 U/ 235 U ratio, producing a 238 U-enriched U(IV) solid. In contrast, other major U reactive transport processes fractionate these isotopes much less. This suggests the potential to quantify the extent of bioreduction occurring in groundwater containing U using the 238 U/ 235 U ratio, which would substantially improve upon current practices largely relying on U concentration measurements alone. Current reactive transport models for uranium dynamics include only concentration measurements, which are strongly influenced by highly coupled reactive transformation and aqueous transport processes. The complex physical and chemical behavior of U potentially compromises such quantitative analysis of U storage and release. Here we report the first numerical reactive transport model which explicitly incorporates variations in the 238 U/ 235 U ratio of U and demonstrates improved interpretation of the principal chemical reactions and groundwater transport processes affecting the subsurface mobility and distribution of this widespread contaminant. Recent U bioreduction studies performed in a contaminated aquifer in Rifle, Colorado, USA applied Rayleigh distillation models to interpret U stable isotope fractionation observed as a result of acetate amendment. These simplified models were unable to resolve the spatiotemporal pattern of U isotope fractionation recorded in the aqueous solutes. Here, we employ the multi-component, isotope-enabled CrunchTope reactive transport software to interpret these measured U isotope ratios, and demonstrate accurate reproduction of observed trends in both geochemistry and 238 U/ 235 U ratios for two consecutive years of field experiments. Overall, our results indicate that accurately modeling both the U concentration and isotope ratio distributions greatly constrains the parameter space of the model. We find that the transport properties of U in the Rifle aquifer are governed by the presence of low-permeability regions, which the isotopes are uniquely sensitive to. When U reduction is spatially constrained by these low-permeability regions, the shift in the 238 U/ 235 U ratio becomes more muted. Accurate modeling of observed U isotope ratios thus provides a powerful means to better understand bioremediation, and the current study serves to advance the application of this novel method.

238U/235U↗
DOE OSTI2025

Durability Research Is Pivotal for Perovskite Photovoltaics

Metal halide perovskite solar cells have shown promising power conversion efficiencies, but commercialization requires that decent durability is also demonstrated. Under normal operation, solar cells are subject to a complex combination of stressors, such as visible light, ultraviolet light, heat, humidity, mechanical stress and electric potential, which complicates the understanding of failure mechanisms. Existing stress tests do not act as a time machine. In new materials systems such as perovskite photovoltaics, the tests have no known relationship to field service. In this Perspective we recommend following a durability learning cycle that interleaves photovoltaic module engineering with field testing; accelerated testing; and preconditioning and performance engineering. We advocate for field testing to demonstrate real-world performance and identify field-relevant failure modes, and urge the community to develop accelerated and qualification tests that account for device metastability, variations in material composition and different/various processing methods. In conclusion, these practices are more difficult, but more important, than the simple pursuit of higher initial efficiencies.

14 SOLAR ENERGY↗
DOE OSTI2021

Effect of metamaterial engineering on the superconductive properties of ultrathin layers of NbTiN

The electronic transport and optical properties of high quality multilayers of NbTiN/AlN with ultrathin NbTiN layers were characterized. The anisotropy of the dielectric function of the multilayers confirmed their hyperbolic metamaterial properties. Here, the superconductive transition temperature, T c , of these engineered superconductors was enhanced up to 32% compared to the T c of a single ultrathin NbTiN layer while the resistivity per NbTiN layer remained unchanged. We have demonstrated that this T c increase can be attributed to enhanced electron–electron interaction in superconducting hyperbolic metamaterials. The measured critical fields are high and have an anomalous temperature dependence on the direction perpendicular to the magnetic field. These results demonstrate that the metamaterial engineering approach can be used to enhance H c2 .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1980

L-band radar sensing of soil moisture

The performance of an L-band, 25 cm wavelength imaging synthetic aperture radar was assessed for soil moisture determination, and the temporal variability of radar returns from a number of agricultural fields was studied. A series of three overflights was accomplished over an agricultural test site in Kern County, California. Soil moisture samples were collected from bare fields at nine sites at depths of 0-2, 2-5, 5-15, and 15-30 cm. These gravimetric measurements were converted to percent of field capacity for correlation to the radar return signal. The initial signal film was optically correlated and scanned to produce image data numbers. These numbers were then converted to relative return power by linear interpolation of the noise power wedge which was introduced in 5 dB steps into the original signal film before and after each data run. Results of correlations between the relative return power and percent of field capacity (FC) demonstrate that the relative return power from this imaging radar system is responsive to the amount of soil moisture in bare fields. The signal returned from dry (15% FC) and wet (130% FC) fields where furrowing is parallel to the radar beam differs by about 10 dB.

Chang, A. T. C.↗
DOE OSTI2021

BETO 2021 Peer Review - Rational Design of Robust Reactor Feeding Systems for Heterogeneous Cellulosic and Agricultural Wastes Based on Biomass Quality Characteristics

Consistent and reliable preprocessing, conveyance, and reactor in-feed systems, particularly for low-cost waste feedstocks, remains a major technical challenge for the emerging Bioeconomy. By identifying critical biomass attributes and connecting them to flow and conversion behavior, science-driven system designs can address these often-overlooked solids handling challenges. The Wonderful Company (TWC) is the world's largest almond and pistachio grower, generating 250,000 dry tons/year of waste material including hulls, shells, and wood (>5 million tons/year industry wide in the U.S.). This project seeks to turn this environmental and economic liability into a sustainable and profitable resource, targeting conversion via gasification to syngas for electricity and bio-char, by addressing related material handling and feeding challenges. Based on optimized preprocessing strategies, bulk material flow, and thermal conversion properties, an overall system design will be developed. The methodology will be tested with FCIC's benchmark loblolly pine residues, to demonstrate the robustness of the overall approach and provide insight and guidance for future systems. The project will culminate in extended field trials to demonstrate an improved continuous feeding system with a commercial biomass-to-electricity gasifier vendor, and an economic analysis demonstrating a reduction in electricity production costs by maximizing on-stream time while minimizing preprocessing and CapEx costs.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2021

Photoinduced Rotation of Colloidal Semiconductor Nanocrystals in an Electric Field

In this work, we demonstrate that solution-phase semiconductor nanocrystals (NCs) undergo photoinduced rotation in an external electric field. Present measurements backed by theoretical calculations show that the rotation of colloidal NCs is driven by the excited-state dipole moment, which is counterbalanced by the solvent viscosity drag. Corresponding angular velocities range from 0.5°/ns for cubic CsPbBr 3 NCs to 3°/ns for nanoparticles with a large photoinduced charge separation (CdSe/CdS core–shell and dot-in-a-rod NCs). Because of photoinduced rotation, solution-phase semiconductor NCs exhibited an order-of-magnitude increase in the spectral changes caused by the quantum confined Stark effect (QCSE), compared to solid NC assemblies. The enhanced QCSE of colloidal NCs reflected their global alignment in solution, which could be retained in a solid environment by slow crystallization. Overall, we expect that the demonstrated phenomenon of the colloidal nanocrystal rotation in an electric field will open up new avenues for developing electro-optical and voltage-sensitive applications.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Mitigating dust particle contamination in an afterglow plasma by controlled lifting with a DC electric field

Abstract Particle contamination due to plasma processing motivates the design of a method of electrically lifting particles in a time interval after a plasma’s power is turned off. Small solid dust particles have electric charges that are not frozen until a late stage of the plasma afterglow. Beyond that time, before they fall to a surface below and cause defects, particles can be lifted in a controlled manner by applying an appropriate direct-current (DC) electric field, as we demonstrate experimentally. A few milliseconds after an argon plasma’s capacitively coupled radio-frequency power is switched off, a vertical DC electric field is applied. Thereafter, video imaging shows that the falling of the particles is slowed or stopped altogether, depending on the magnitude of the upward electric force.

Physics↗
DOE OSTI2020

Southeast Regional CO 2 Utilization and Storage Acceleration Partnership (SECARB-USA): Preliminary Regional Assessment of Potential Storage Complexes, Including Capacities and Costs, Based on Application of NRAP and SCO2T (Deliverable 3.3) Storage Complexes

The Recipient will assist with the field validation of one or more risk assessment toolsets through: 1) collaborative research; 2) sharing of relevant datasets, information, and technical insights from field efforts; and 3) other modeling and simulation toolsets as they are developed. Collaborative research could include, but is not limited to: 1) demonstrating use of field data for improved leakage pathway characterization, uncertainty reduction, and risk management and uncertainty workflows; 2) testing and validation of a specific National Risk Assessment Partnership (NRAP) tool using site specific data; and 3) improved modeling or reduced-order modeling of geophysical monitoring.

42 ENGINEERING↗
NASA NTRS1975

A model of coronal holes

It has been noted that coronal holes appear to be associated with regions of diverging magnetic field in the corona. We set out to test the hypothesis that coronal holes may be caused by an increased flow of energy into the solar wind resulting directly from this diverging magnetic field pattern. Simple models were devised to approximate the energy flow down into the transition region and up into the solar wind as a function of the temperature, density, and rate of field line divergence in the corona. By assuming the rate of mechanical energy influx into the corona to be constant, it was then possible to solve numerically for the coronal temperature and density as a function of the rate of field line divergence. The results of these calculations demonstrate that a diverging field pattern can, indeed, bring about reductions in the temperature and density at the base of the corona comparable to those observed in coronal holes.

Adams, W. M.↗
NASA NTRS1977

Evaluation of coated columbium alloy heat shields for space shuttle thermal protection system application

A three-phase program to develop and demonstrate the feasibility of a metallic heat shield suitable for use on Space Shuttle Orbiter class vehicles at operating surface temperatures of up to 1590 K (2400 F) is summarized. An orderly progression of configuration studies, material screening tests, and subscale structural tests was performed. Scale-up feasibility was demonstrated in the final phase when a sizable nine-panel array was fabricated and successfully tested. The full-scale tests included cyclic testing at reduced air pressure to 1590 K (2400 F) and up to 158 dB overall sound pressure level. The selected structural configuration and design techniques succesfully eliminated thermal induced failures. The thermal/structural performance of the system was repeatedly demonstrated. Practical and effective field repair methods for coated columbium alloys were demonstrated. Major uncertainties of accessibility, refurbishability, and durability were eliminated.

Black, W. E.↗
NASA NTRS1987

Nonuniform sampling techniques for antenna applications

A two-dimensional sampling technique, which can employ irregularly spaced samples (amplitude and phase) in order to generate the complete far-field patterns is presented. The technique implements a matrix inversion algorithm, which depends only on the nonuniform sampled data point locations and with no dependence on the actual field values at these points. A powerful simulation algorithm is presented to allow a real-life simulation of many reflector/feed configurations and to determine the usefulness of the nonuniform sampling technique for the copolar and cross-polar patterns. Additionally, an overlapped window concept and a generalized error simulation model are discussed to identify the stability of the technique for recovering the field data among the nonuniform sampled data. Numerical results are tailored for the pattern reconstruction of a 20-m offset reflector antenna operating at L-band. This reflector is planned to be used in a proposed measurement concept of large antenna aboard the Space Shuttle, whereby it would be almost impractical to accurately control the movement of the Shuttle with respect to the RF source in prescribed directions in order to generate uniform sampled points. Also, application of the nonuniform sampling technique to patterns obtained using near-field measured data is demonstrated. Finally, results of an actual far-field measurement are presented for the construction of patterns of a reflector antenna from a set of nonuniformly distributed measured amplitude and phase data.

Rahmat-Samii, Yahya↗
NASA NTRS1998

Use of Microgravity to Control the Microstructure of Eutectics

This grant began in June of 1996. Its long term goal is to be able to control the microstructure of directionally solidified eutectic alloys, through an improved understanding of the influence of convection. The primary objective of the present projects is to test hypotheses for the reported influence of microgravity on the microstructure of three fibrous eutectics (MnBi-Bi, InSb-NiSb, Al3Ni-Al). A secondary objective is to determine the influence of convection on the microstructure of other eutectic alloys. Two doctoral students and a masters student supported as a teaching assistant were recruited for this research. Techniques were developed for directional solidification of MnBi-Bi eutectics with periodic application of current pulses to produce an oscillatory freezing rate. Image analysis techniques were developed to obtain the variation in MnBi fiber spacing, which was found to be normally distributed. The mean and standard deviation of fiber spacing were obtained for several freezing conditions. Eighteen ampoules were prepared for use in the gradient freeze furnace QUELD developed at Queen's University for use in microgravity. Nine of these ampoules will be solidified soon at Queen's in a ground-based model. We hope to solidify the other nine in the QUELD that is mounted on the Canadian Microgravity Isolation Mount on MIR. Techniques are being developed for directional solidification of the Al-Si eutectic at different freezing rates, with and without application of accelerated crucible rotation to induce convection. For the first time, theoretical methods are being developed to analyze eutectic solidification with an oscillatory freezing rate. In a classical sharp-interface model, we found that an oscillatory freezing rate increases the deviation of the average interfacial composition from the eutectic, and increases the undercooling of the two phases by different amounts. This would be expected to change the volume fraction solidifying and the fiber spacing. Because of difficulties in tracking the freezing interfaces of the two solid phases, a phase-field model is also being developed. A paper demonstrating application of phase field methods to periodic structures has been submitted for publication.

Wilcox, William R.↗
NASA NTRS2008

The Heliospheric Magnetic Field Over the Hale Cycle

The concept that open magnetic flux of the Sun (rooted with one and only one footpoint at the Sun) is a conserved quantity is taking root in the heliospheric community. Observations show that the Sun's open magnetic flux returns to the baseline from one solar minimum to the next. The temporary enhancement in the 1AU heliospheric magnetic flux near solar maximum can be accounted for by the temporary creation of closed magnetic flux (with two footpoints at the Sun) during the ejection of coronal mass ejections (CMEs), which are more frequent near solar maximum. As a part of the International Heliophysical Year activities, this paper reviews two recently discussed consequences of open flux conservation: the reversal of open magnetic flux over the solar cycle driven by Coronal Mass Ejections and the impacts of open flux conservation on the global structure of the heliospheric magnetic field. These studies demonstrate the inherent linkages between coronal mass ejections, footpoint motions back at the Sun, and the global structure and evolution of the heliospheric magnetic field.

Schwardron, N. A.↗