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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Investigation of a Solid-State Tuning Behavior in Lithium Niobate

Electric field-based frequency tuning of acoustic resonators at the material level provides an enabling technology for building complex tunable filters. Tunable acoustic resonators were fabricated in thin plates (h/λ ~ 0.05) of X-cut lithium niobate (90°, 90°, ψ = 170°). Lithium niobate is known for its large electromechanical coupling (SH: K 2 40%) and thus applicability for low-insertion loss and wideband filter applications. We demonstrate the effect of a DC bias to shift the resonant frequency by ~0.4% by directly tuning the resonator material. The mechanism is based on the nonlinearities that exist in the piezoelectric properties of lithium niobate. Devices centered at 332 MHz achieved frequency tuning of 12 kHz/V through application of a DC bias.

47 OTHER INSTRUMENTATION↗
DOE OSTI2014

Functional approach to exploring climatic and landscape controls of runoff generation: 1. Behavioral constraints on runoff volume

Abstract Inspired by the Dunne diagram, the climatic and landscape controls on the partitioning of annual runoff into its various components (Hortonian and Dunne overland flow and subsurface stormflow) are assessed quantitatively, from a purely theoretical perspective. A simple distributed hydrologic model has been built sufficient to simulate the effects of different combinations of climate, soil, and topography on the runoff generation processes. The model is driven by a sequence of simple hypothetical precipitation events, for a large combination of climate and landscape properties, and hydrologic responses at the catchment scale are obtained through aggregation of grid‐scale responses. It is found, first, that the water balance responses, including relative contributions of different runoff generation mechanisms, could be related to a small set of dimensionless similarity parameters. These capture the competition between the wetting, drying, storage, and drainage functions underlying the catchment responses, and in this way, provide a quantitative approximation of the conceptual Dunne diagram. Second, only a subset of all hypothetical catchment/climate combinations is found to be “behavioral,” in terms of falling sufficiently close to the Budyko curve, describing mean annual runoff as a function of climate aridity. Furthermore, these behavioral combinations are mostly consistent with the qualitative picture presented in the Dunne diagram, indicating clearly the commonality between the Budyko curve and the Dunne diagram. These analyses also suggest clear interrelationships amongst the “behavioral” climate, soil, and topography parameter combinations, implying these catchment properties may be constrained to be codependent in order to satisfy the Budyko curve.

Li, Hong‐Yi↗
DOE OSTI2017

Bicomponent Block Copolymers Derived from One or More Random Copolymers as an Alternative Route to Controllable Phase Behavior

Block copolymers have been extensively studied due to their ability to spontaneously self-organize into a wide variety of morphologies that are valuable in energy-, medical- and conservation-related (nano)technologies. While the phase behavior of bicomponent diblock and triblock copolymers is conventionally governed by temperature and individual block masses, we demonstrate that their phase behavior can alternatively be controlled through the use of blocks with random monomer sequencing. Block random copolymers (BRCs), i.e., diblock copolymers wherein one or both blocks is a random copolymer comprised of A and B repeat units, have been synthesized, and their phase behavior, expressed in terms of the order-disorder transition (ODT), has been investigated. Our results establish that, depending on the block composition contrast and molecular weight, BRCs can microphase-separate. We also report that the predicted ODT can be generated at relatively constant molecular weight and temperature with these new soft materials. This sequence-controlled synthetic strategy is extended to thermoplastic elastomeric triblock copolymers differing in chemistry and possessing a random-copolymer midblock.

Ashraf, Arman R.↗
DOE OSTI2014

A Composite Modeling Analysis of the Deformation Behavior of Medium Manganese Steels

The deformation behavior of medium manganese steels was evaluated with uniaxial tensile testing and the results were correlated with predictions of a composite model shown previously to provide design insight into the development of multi-phase steels with third-generation advanced high strength steel (3GAHSS) properties. An equilibrium thermodynamic-based methodology to design microstructures containing systematic amounts of metastable austenite with controlled stability against transformation is presented. The analysis is based on Mn enrichment of austenite during intercritical annealing of medium Mn (7 and 10 wt pct.) low carbon (0.1 and 0.15 wt pct) steels. The steels were produced as laboratory heats that were hot and cold rolled prior to annealing. After annealing the microstructures consisted primarily of either a matrix of fine grained ferrite with austenite contents between 32.6 and 45.2 wt pct (7Mn, 0.1C steels) or a matrix of martensite with various amounts of austenite in the higher Mn steel. The different intercritical annealing conditions produced steels with wide variations in austenite contents and austenite compositions (Mn and C contents) resulting in steels with significant variations in austenite stability. Predictions based on the composite analysis with different assumed flow behaviors for the individual constituents and stability functions for the meta-stable austenite are presented and shown to accurately predict strength-ductility combinations over a range of austenite volume fractions for the 7Mn steel. Applicability of the composite analysis is extended to consider the deformation behavior of the 10Mn steel and evaluate other possible microstructural combinations leading to 3GAHSS properties.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Vortex jump behavior in coupled nanomagnetic heterostructures

The spin configuration and magnetic behavior in patterned nanostructures can be controlled by manipulating the interplay between the competing energy terms. This in turn requires fundamental knowledge of the magnetic interactions at the local nanometer scale. Here in this article, we report on the spin structure and magnetization behavior of patterned discs containing exchange coupled ferromagnetic layers with additional exchange bias to an antiferromagnetic layer. The magnetization reversal was explored by direct local visualization of the domain behavior using in-situ Lorentz transmission electron microscopy, from which quantitative magnetic induction maps were reconstructed. The roles of the main competing energy terms were elucidated and the reversal mechanism was identified as a coupled phenomenon of incoherent rotation in the exchange-biased layer and localized vortex nucleation and discontinuous propagation in the free layer, including an anomalous jump in the trajectory. The observations were supported by micromagnetic simulations and modeled phase shift simulations. In conclusion, the work presented here provides fundamental insights into opportunities for macroscopic control of the energy landscape of magnetic heterostructures for functional applications.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Insights from Smart Meters. Identifying Specific Actions, Behaviors and Characteristics that drive savings in Behavior-Based Programs

In this report, we use smart meter data to analyze specific actions, behaviors, and characteristics that drive energy savings in a behavior-based (BB) program. Specifically, we examine a Home Energy Report (HER) program. These programs typically obtain 1% to 3% annual savings, and recent studies have shown hourly savings of between 0.5% and 3%. But what is driving these savings? What types of households tend to be “high-savers”, and what behaviors are they adopting? There are several possibilities: one-time behaviors (e.g., changing thermostat settings); reoccurring habitual behaviors (e.g., turning off lights); and equipment purchase behaviors (e.g., energy efficient appliances), and these may vary across households, regions, and over time.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2014

Insights from Smart Meters: Identifying Specific Actions, Behaviors, and Characteristics That Drive Savings in Behavior-Based Programs

In this report, we use smart meter data to analyze specific actions, behaviors, and characteristics that drive energy savings in a BB program. Specifically, we examine a Home Energy Report (HER) program. These programs typically obtain 1% to 3% annual savings, and recent studies have shown hourly savings of between 0.5% and 3%.1 But what is driving these savings? What types of households tend to be “high-savers,” and what behaviors are they adopting? There are several possibilities: one-time behaviors (e.g., changing thermostat settings), reoccurring habitual behaviors (e.g., turning off lights), and equipment purchase behaviors (e.g., energy efficient appliances); these may vary across households, regions, and over time.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2018

Rate theory scenarios study on fission gas behavior of U 3 Si 2 under LOCA conditions in LWRs

Fission gas behavior of U3Si2 under various loss-of-coolant accident (LOCA) conditions in light water reactors (LWRs) was simulated using rate theory. A rate theory model for U3Si2 that covers both steady-state operation and power transients was developed for the GRASS-SST code based on existing research reactor/ion irradiation experimental data and theoretical predictions of density functional theory (DFT) calculations. The steady-state and LOCA condition parameters were either directly provided or inspired by BISON simulations. Due to the absence of in-pile experiment data for U3Si2's fuel performance under LWR conditions at this stage of accident tolerant fuel (ATF) development, a variety of LOCA scenarios were taken into consideration to comprehensively and conservatively evaluate the fission gas behavior of U3Si2 during a LOCA.

Miao, Yinbin (ORCID:0000000231284275)↗
DOE OSTI2016

Evaluation of Knock Behavior for Natural Gas - Gasoline Blends in a Light Duty Spark Ignited Engine

The compression ratio is a strong lever to increase the efficiency of an internal combustion engine. However, among others, it is limited by the knock resistance of the fuel used. Natural gas shows a higher knock resistance compared to gasoline, which makes it very attractive for use in internal combustion engines. The current paper describes the knock behavior of two gasoline fuels, and specific incylinder blend ratios with one of the gasoline fuels and natural gas. The engine used for these investigations is a single cylinder research engine for light duty application which is equipped with two separate fuel systems. Both fuels can be used simultaneously which allows for gasoline to be injected into the intake port and natural gas to be injected directly into the cylinder to overcome the power density loss usually connected with port fuel injection of natural gas. Adding natural gas at wide open throttle helps to reduce knock mitigating measures and increases the efficiency and power density compared to the other gasoline type fuels with lower knock resistance. The used methods, knock intensity and number of pressure waves, do not show significant differences in knock behavior for the natural gas - gasoline blends compared to the gasoline type fuels. A knock integral was used to describe the knock onset location of the fuels tested. Two different approaches were used to determine the experimental knock onset and were compared to the knock onset delivered by the knock integral (chemical knock onset). The gasoline type fuels show good agreement between chemical and experimental knock onset. However, the natural gas -gasoline blends show higher discrepancies comparing chemical and experimental knock onset.

Advanced Combustion Concept↗
DOE OSTI2018

Migratory Behavior and Physiological Development as Potential Determinants of Life History Diversity in Fall Chinook Salmon in the Clearwater River

We studied the influence of behavior, water velocity, and physiological development on the downstream movement of subyearling fall Chinook Salmon Oncorhynchus tshawytscha in free-flowing and impounded reaches of the Clearwater and Snake rivers as potential mechanisms that might explain life history diversity in this stock. Movement rates and the percentage of radio-tagged fish that moved faster than the average current velocity were highest in the free-flowing Clearwater River compared to impounded reaches. This provided support for our hypothesis that water velocity is a primary determinant of downstream movement regardless of a fish’s physiological development. In contrast, movement rates slowed and detections became fewer in impounded reaches where velocities were much lower. The percentage of fish that moved faster than the average current velocity continued to decline and reached zero in the lower-most reach of Lower Granite Reservoir suggesting that behavioral disposition to move downstream was low. These findings contrast those of a similar, previous study of Snake River subyearlings in spite of hydrodynamic conditions being similar. Physiological differences between Snake and Clearwater river migrants shed light on this disparity. Subyearlings from the Clearwater River were parr-like in their development and never showed an increase in gill Na+/K+-ATPase activity as did smolts from the Snake River. The later emergence timing and cooler rearing temperatures in the Clearwater River may suppress normal physiological development that causes many fish to delay downstream movement and adopt a yearling life history strategy.

Tiffan, Kenneth F.↗
DOE OSTI2022

Understanding the Origin of the Nonpassivating Behavior of Si-Based Anodes during the Initial Cycles

In this contribution, we combined electrochemical cycling and X-ray photoelectron spectroscopy (XPS) to understand the nonpassivating behavior of the solid electrolyte interphase (SEI) on Si anodes during the first cycles. Based on galvanostatic measurements, we show that the irreversible capacity loss is reduced after the first cycle, and it stays almost constant from the second cycle onwards. XPS was used to determine the root causes of the Coulombic inefficiency, showing that the rate of decomposition of the organic solvents strongly decreased after the first cycle, whereas the rate of salt decomposition is almost unchanged between cycles. We determine that the inhibition of the decomposition reaction of the organic solvent is responsible for the lower Coulombic loss during the second electrochemical cycle in comparison to the first, whereas the nonpassivating behavior toward the salt decomposition is one of the main causes of capacity loss upon cycling. Here, we further revisit the role of cracking in contributing to capacity loss. Whereas high volumetric expansion remains an issue plaguing the performance of Si anodes, our chronoamperometry studies reveal that the SEI formed on Si anodes does not passivate even when the electrode is fully expanded, and no additional surface is exposed. Overall, our work establishes the need to address the chemical and electrochemical instability of the SEI on the Si anode in addition to the more notorious issue of cracking.

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

Native defects and impurity band behavior in half-Heusler thermoelectric NbFeSb

To investigate the electronic behavior and magnetic properties of NbFeSb, we have performed 93 Nb NMR, specific heat and magnetic measurements on NbFeSb samples heat treated at high temperatures. In this work, magnetic measurements combined with an observed Schottky anomaly and changes in the NMR line width indicate the presence of a 0.2% concentrated native magnetic defect in stoichiometric NbFeSb samples. The origin of these native defects is believed to be due to Fe antisites on Nb sites. In addition, NMR shift and spin–lattice relaxation results below 200 K reveal a Korringa-like response indicating heavily-doped p-type behavior due to native defects. Above 280 K, this converts to an activated behavior, indicating the presence of an impurity band, empty at low temperatures, which is located around 0.03 eV above the valence band maximum.

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

Generalized gradient approximation exchange energy functional with correct asymptotic behavior of the corresponding potential

A new non-empirical exchange energy functional of the generalized gradient approximation (GGA) type, which gives an exchange potential with the correct asymptotic behavior, is developed and explored. In combination with the Perdew-Burke-Ernzerhof (PBE) correlation energy functional, the new CAP-PBE (CAP stands for correct asymptotic potential) exchange-correlation functional gives heats of formation, ionization potentials, electron affinities, proton affinities, binding energies of weakly interacting systems, barrier heights for hydrogen and non-hydrogen transfer reactions, bond distances, and harmonic frequencies on standard test sets that are fully competitive with those obtained from other GGA-type functionals that do not have the correct asymptotic exchange potential behavior. Distinct from them, the new functional provides important improvements in quantities dependent upon response functions, e.g., static and dynamic polarizabilities and hyperpolarizabilities. CAP combined with the Lee-Yang-Parr correlation functional gives roughly equivalent results. Consideration of the computed dynamical polarizabilities in the context of the broad spectrum of other properties considered tips the balance to the non-empirical CAP-PBE combination. Intriguingly, these improvements arise primarily from improvements in the highest occupied and lowest unoccupied molecular orbitals, and not from shifts in the associated eigenvalues. Those eigenvalues do not change dramatically with respect to eigenvalues from other GGA-type functionals that do not provide the correct asymptotic behavior of the potential. Unexpected behavior of the potential at intermediate distances from the nucleus explains this unexpected result and indicates a clear route for improvement.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

X-ray imaging for studying behavior of liquids at high pressures and high temperatures using Paris-Edinburgh press

Several X-ray techniques for studying structure, elastic properties, viscosity, and immiscibility of liquids at high pressures have been integrated using a Paris-Edinburgh press at the 16-BM-B beamline of the Advanced Photon Source. In this paper, we report the development of X-ray imaging techniques suitable for studying behavior of liquids at high pressures and high temperatures. White X-ray radiography allows for imaging phase separation and immiscibility of melts at high pressures, identified not only by density contrast but also by phase contrast imaging in particular for low density contrast liquids such as silicate and carbonate melts. In addition, ultrafast X-ray imaging, at frame rates up to ~10 5 frames/second (fps) in air and up to ~10 4 fps in Paris-Edinburgh press, enables us to investigate dynamics of liquids at high pressures. Very low viscosities of melts similar to that of water can be reliably measured. These high-pressure X-ray imaging techniques provide useful tools for understanding behavior of liquids or melts at high pressures and high temperatures.

47 OTHER INSTRUMENTATION↗