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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 397 records · Page 22

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NASA NTRS1978

Period variations in pulsating X-ray sources. I - Accretion flow parameters and neutron star structure from timing observations

Torque fluctuations which can lead to variations in the periods of pulsating X-ray sources are examined. A description of torque variations in terms of noise processes is developed, and the resulting noise models are applied to observations of several pulsating X-ray sources. It is shown that fluctuations in accretion torque could account for the observed period variations and spindown episodes in Her X-1 and Cen X-3. The values of the torque noise strengths inferred from either a nonresonant response or, in the case of Her X-1, a Tkachenko-mode interpretation of the data are found to be consistent with those expected from processes at the magnetospheric boundary of an accreting neutron star. Ways to distinguish among the various interpretations of the period variations are considered. It is noted that fluctuating mass-flow rates may be responsible for other phenomena observed in compact X-ray sources, such as wobble with zero initial amplitude and binary period variations in close binary systems experiencing mass transfer.

Lamb, F. K.↗

DOE OSTI2026

Innovations in underground hydrogen storage with multiphysics simulations, optimization, and monitoring: A review

Underground Hydrogen Storage (UHS) is a promising solution for large-scale energy storage and a critical component in advancing low-carbon energy system. Ensuring the safety and efficiency of UHS necessitates a comprehensive understanding of multiphysical interactions driven by cyclic pore fluid pressure fluctuations and coupled physicochemical processes. Here, this review examines the key geomechanical responses in UHS, including rock property variations under cyclic loading, fracture evolution and propagation, reservoir stress sensitivity, and fault stability. It also explores the impact of geochemical and microbial reactions on geomechanical characteristics. We provide an in-depth analysis of Thermal-Hydraulic-Mechanical-Chemical (THMC) coupled numerical simulations, highlighting their potential for future multi-scale modeling. Limitations of current machine learning (ML) approaches in addressing UHS challenges are highlighted, emphasizing the need for innovative ML-based methodologies. Operational strategies for hydrogen injection and production are reviewed, focusing on safety, efficiency, and economic viability. The necessity for multi-objective optimization (MOO) to balance storage efficiency, risk mitigation, and cost-effectiveness is also discussed. Current monitoring technologies are evaluated to ensure safe and efficient UHS operations. Finally, this review identifies critical knowledge gaps and underscores the importance of advancing geomechanical understanding under multiphysics-coupling. We highlight the need for ML-driven multiphysics theories, enhanced modeling techniques, and robust optimization strategies to improve UHS performance. This study serves as a comprehensive reference for future research and the large-scale implementation of UHS systems.

25 ENERGY STORAGE↗

DOE OSTI2025

Pressure-induced structural and dielectric changes in liquid water at room temperature

Understanding the pressure-dependent dielectric properties of water is crucial for a wide range of scientific and practical applications. In this study, we employ a deep neural network trained on density functional theory data to investigate the dielectric properties of liquid water at room temperature across a pressure range of 0.1–1000 MPa. We observe a nonlinear increase in the static dielectric constant ɛ 0 with increasing pressure, a trend that is qualitatively consistent with experimental observations. This increase in ɛ 0 is primarily attributed to the increase in water density under compression, which enhances collective dipole fluctuations within the hydrogen-bonding network as well as the dielectric response. Despite the increase in ɛ 0 , our results reveal a decrease in the Kirkwood correlation factor G K with increasing pressure. Furthermore, this decrease in G K is attributed to pressure-induced structural distortions in the hydrogen-bonding network, which weaken dipolar correlations by disrupting the ideal tetrahedral arrangement of water molecules.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2021

Dancing Droplets on a Defect Line [Poster]

Liquid crystalline (LC) phases are made up of molecules or other small units that organize into mesoscale assemblies. Their order resembles that of crystalline solids, but since the molecules have some freedom to move position and direction, these assemblies also behave like liquids. Thus, highly birefringent and responsive phases with many defect (or disclination) lines can emerge. These ever fluctuating lines indicate regions of the LC where the position of the molecules disrupt the local rotational symmetry within the phase.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1975

Comparison of vibrations of a combination of solid-rocket launch vehicle and payload during a ground firing and launching

The results of a study into the environmental vibrations of a payload mounted on the Nike rocket launch vehicle were presented. Data were obtained during the flight acceptance test of the payload, the firing of the total vehicle in a special test stand, and the powered and unpowered flights of the vehicle. The vibrational response of the structure was measured. Data were also obtained on the fluctuating pressure on the outside surface of the vehicle and inside the forward and after ends of the rocket chamber. A comparison of the data from the three test conditions indicated that external pressure fluctuations were the major source of vibrations in the payload area, and pressure fluctuations within the rocket motor were the major source of vibrations contiguous to the payload area.

Schoenster, J. A.↗

NASA NTRS1986

Transverse acceleration of oxygen ions by electromagnetic ion cyclotron resonance with broad band left-hand polarized waves

Central plasma sheet (CPS) ion conics are oxygen-dominated, with peak energies ranging from tens to hundreds of eV centered around pitch-angles between 115 and 130 degrees. Because of the lack of correlation between the CPS conics and the observed currents and/or electron beam-like structures, it is not likely that all of these conics are generated by interactions with electrostatic ion cyclotron waves or lower hybrid waves. Instead, it is suggested that the observed intense broad band electric field fluctuations in the frequency range between 0 and 100 Hz can be responsible for the transverse energization of the ions through cyclotron resonance heating with the left-hand polarized electromagnetic waves. This process is much more efficient for heating the oxygen ions than hydrogen ions, thus providing a plausible explanation of the oxygen dominance in CPS conics. Simple algebraic expressions are given from which estimates of conic energy and pitch angle can be easily calculated. This suggested mechanism can also provide some preheating of the oxygen ions in the boundary plasma sheet (BPS) where discrete aurorae form.

Chang, T.↗

NASA NTRS1986

The response of energetic particles to nightside magnetic pulsations as seen by AMPTE/CCE

This paper reports the response of energetic ions during two types of magnetic oscillations: an azimuthal fluctuation and a radial fluctuation, both with periods in the Pc4-Pc5 range. The azimuthal oscillations occur on April 30, 1985 from 0950 to 1210 UT at 8.7 to 7.0 R(E) and from 1.5 to 2.8 MLT. The radial oscillations occur on April 26, 1985 from 1200 to 1400 UT at 8.7 to 7.5 R(E) and from 2.2 to 3.0 MLT. In this case the particles show in phase periodic flux variations in sectors with radial gradients in the flux. These particle fluctuations represent two distinct modulations, each associated with a basic mode of magnetic oscillation in the near-earth magnetotail.

Lopez, R. E.↗

NASA NTRS2016

Response of the Equatorial Ionosphere to the Geomagnetic DP 2 Current System

The response of equatorial ionosphere to the magnetospheric origin DP 2 current system fluctuations is examined using ground-based multiinstrument observations. The interaction between the solar wind and fluctuations of the interplanetary magnetic field (IMF) Bz, penetrates nearly instantaneously to the dayside equatorial region at all longitudes and modulates the electrodynamics that governs the equatorial density distributions. In this paper, using magnetometers at high and equatorial latitudes, we demonstrate that the quasiperiodic DP 2 current system penetrates to the equator and causes the dayside equatorial electrojet (EEJ) and the independently measured ionospheric drift velocity to fluctuate coherently with the high-latitude DP 2 current as well as with the IMF Bz component. At the same time, radar observations show that the ionospheric density layers move up and down, causing the density to fluctuate up and down coherently with the EEJ and IMF Bz.

Yizengaw, E.↗

NASA NTRS1988

Temperature Fluctuations During Crystal Growth

Technique developed to deconvolve period and relative amplitude of fluctuations of heat flow inBridgman crystal growth. Temperature-measuring device with enough sensitivity and frequency response to make desired measurements inserted close as possible to substance monitored. Time-dependent temperature response recorded, and time domain response converted to frequency domain for further analysis. Fast fourier transform (FFT) of data on temperature oscillations shows particular behavior at some specific frequencies corresponding with striations, or defects observed on crystal. Useful procedure to help determine sources of some growth-induced crystalline defects. Other processes sensitive to small temperature fluctuations, such as diffusion, precipitation, and corrsion, benefit from technique.

Fripp, Archibald L., Jr.↗

DOE OSTI2023

Ice phonon spectra and Bayes inference: A gateway to a new understanding of terahertz sound propagation in water

Understanding how molecules engage in collective motions in a liquid where a network of bonds exists has both fundamental and applied relevance. On the one hand, it can elucidate the “ordering” role of long-range correlations and inspire new avenues to control such order to implement sound manipulation. Water represents an ideal investigation case to unfold these general aspects, and, across the decades, it has been the focus of thorough scrutiny. Further, despite this investigative effort, the spectrum of terahertz density fluctuations of water largely remains a puzzle for condensed matter physicists. To unravel it, we compare previous scattering measurements of water spectra with new ones on ice. Owing to the unique asset of Bayesian inference, we draw a more detailed portrayal of the phonon response of ice. The comparison with the one of liquid water challenges the current understanding of density fluctuations in water, or more in general, of any networked liquid.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1988

Computer simulations of two-pickup-ion instabilities in a cometary environment

This paper presents a one-dimensional electromagnetic hybrid computer simulation of distant cometary environments, in which protons and oxygen ions are injected continuously at the same time. It is demonstrated that, when, instead of a single component, both protons and oxygen ions are injected, the faster growing shorter-wavelength proton-proton right-hand resonant instability dominates the early time physics, leading to linear temporal growth of the fluctuating magnetic field energy density and pitch angle scattering of the protons (but causing no significant response by the nonresonant oxygen ions). At later times, as the injected oxygen ions accumulate sufficient density, the oxygen-proton right-hand resonant instability emerges, exhibiting exponential temporal growth to a relatively large peak amplitude, phase bunching, and magnetically trapping the oxygen ions. At times after peak amplitude, the oxygen-proton fluctuations stochastically accelerate some of the injected protons.

Gary, S. Peter↗

DOE OSTI2021

Role of generic scale invariance in a Mott transition from a U(1) spin-liquid insulator to a Landau Fermi-liquid metal

Highlights: • We look at the role played by generic scale invariance (GSI) in the phase transition between a U(1) spin liquid and a Fermi liquid. • We identify dangerously irrelevant operators in the renormalization group transformation, involved with the GSI. • We highlight novel mean-field dynamics of this Mott quantum criticality, resulting from the GSI. We investigate the role of generic scale invariance in a Mott transition from a U(1) spin-liquid insulator to a Landau Fermi-liquid metal, where there exist massless degrees of freedom in addition to quantum critical fluctuations. Here, the Mott quantum criticality is described by critical charge fluctuations, and additional gapless excitations are U(1) gauge-field fluctuations coupled to a spinon Fermi surface in the spin-liquid state, which turn out to play a central role in the Mott transition. An interesting feature of this problem is that the scaling dimension of effective leading local interactions between critical charge fluctuations differs from that of the coupling constant between U(1) gauge fields and matter-field fluctuations in the presence of a Fermi surface. As a result, there appear dangerously irrelevant operators, which can cause conceptual difficulty in the implementation of renormalization group (RG) transformations. Indeed, we find that the curvature term along the angular direction of the spinon Fermi surface is dangerously irrelevant at this spin-liquid Mott quantum criticality, responsible for divergence of the self-energy correction term in U(1) gauge-field fluctuations. Performing the RG analysis in the one-loop level based on the dimensional regularization method, we reveal that such extremely overdamped dynamics of U(1) gauge-field fluctuations, which originates from the emergent one-dimensional dynamics of spinons, does not cause any renormalization effects to the effective dynamics of both critical charge fluctuations and spinon excitations. However, it turns out that the coupling between U(1) gauge-field fluctuations and both matter-field excitations still persists at this Mott transition, which results in novel mean-field dynamics to explain the nature of the spin-liquid Mott quantum criticality. We discuss physical implications of effective one-dimensional spin dynamics and extremely overdamped gauge dynamics at the Mott quantum criticality.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Feasibility Study of Real-Time Carbon Emission Responsive Electric Vehicle Charging Control in Buildings: Preprint

With the progressing electrification of the transportation sector, the source of carbon emissions is gradually shifting from fossil fuel to grid electricity because of electric vehicles (EVs). The carbon intensity of the grid can fluctuate significantly within hours due to the time-varying power generation mix. Therefore, shifting EV charging loads to cleaner hours in response to the carbon intensity signals can reduce carbon emissions. Existing EV charging control methods typically consider the electricity price or the available generation by distributed energy resources (e.g., photovoltaics) to inform decision-making. Such methods tend to reduce energy costs but may neglect the environmental impact of EV charging activities. We propose and compare four carbon emission responsive EV charging controllers with various control rules. The proposed controllers are evaluated based on simulation experiments using metrics such as carbon emission reduction potential, state of charge (SOC) at departure, and peak demand. We found that the need of EV owners to have full batteries at departure could lead to an emission increase when the curtailed EV charge was compensated before departure. Further, up to 12.7% of carbon emission reduction can be achieved if the EV owners reduce the target SOC at departure by less than 15%.

carbon emission↗

DOE OSTI2023

Kinetics of the xanthophyll cycle and its role in photoprotective memory and response

Efficiently balancing photochemistry and photoprotection is crucial for survival and productivity of photosynthetic organisms in the rapidly fluctuating light levels found in natural environments. The ability to respond quickly to sudden changes in light level is clearly advantageous. In the alga Nannochloropsis oceanica we observed an ability to respond rapidly to sudden increases in light level which occur soon after a previous high-light exposure. This ability implies a kind of memory. In this work, we explore the xanthophyll cycle in N. oceanica as a short-term photoprotective memory system. By combining snapshot fluorescence lifetime measurements with a biochemistry-based quantitative model, we show that short-term memory arises from the xanthophyll cycle. In addition, the model enables us to characterize the relative quenching abilities of the three xanthophyll cycle components. Given the ubiquity of the xanthophyll cycle in photosynthetic organisms the model described here will be of utility in improving our understanding of vascular plant and algal photoprotection with important implications for crop productivity.

59 BASIC BIOLOGICAL SCIENCES↗

NASA NTRS1970

Heat-resistant pressure probe with high-frequency response

Probe, having a sensor at its inner tip in intimate contact with pressure transients, measures pressure wave fluctuations through an engine's combustion chamber. A film of flexible opaque material on the face of the sensor prevents high radiation fluxes from heating the quartz crystal and thus changing the electrical characteristics.

Rogero, R. S.↗

DOE OSTI2021

Acoustic gas volume fraction measurement in a multiphase flowing liquid

Apparatus and methods for the measurement of gas volume fraction of produced oil are described. A first method measures the response of a pipe containing the produced oil excited by a source of vibration in the form of an acoustic frequency chirp containing a linearly varying range of frequencies in the tens of kilohertz range encompassing at least one resonant mode of the pipe. As the gas volume fraction increases, the location of the peak maximum of the measured frequency spectrum responsive to the excitation increases in frequency, and the height of the peak maximum increases, thereby permitting a linear calibration curve to be obtained. A second method measures the response of a pipe containing the produced oil to excitation by a continuous source of vibration having a chosen frequency above those which excite flexural vibrations in the pipe and simultaneously excite acoustic waves in the fluid contained in the pipe, known as the coincidence frequency. Gas present in the fluid will interrupt sound propagation or reverberation, thereby generating fluctuations in the amplitude of the measured vibrations of the pipe. The amplitude fluctuation level provides a measure of the gas volume present inside the pipe. A third method measures the response of a pipe containing the produced oil to excitation by a high-bandwidth, short pulse having a chosen center frequency above the coincidence frequency. Gas present in the fluid will interrupt pulse propagation, thereby generating fluctuations in the amplitude of the measured vibrations of the pipe.

Sinha, Dipen N.↗

NASA NTRS1976

Measured response of a complex structure to supersonic turbulent boundary layers

Measurements of the response of a large frame-stringer panel excited by supersonic turbulent boundary layer are reported. The statistical description of the wall pressure fluctuations in terms of the mean flow parameters governing the turbulent boundary layer is given. These results can be used in the development of design criteria on the response of sidewall structure of a large airplane in supersonic flight, since both forcing field and structure are realistic. Results indicate the significant importance of the modal coupling and the acoustic damping. The acoustic damping plays a major role in the response of the structure.

Maestrello, L.↗

NASA NTRS2021

Rotorcraft Sound Quality Metric Test 1: Stimuli Generation and Supplemental Analyses

A psychoacoustic test was conducted at the NASA Langley Research Center Exterior Effects Room (EER) to assess annoyance to simulated helicopter sounds over a range of sound quality (SQ) metric values. Initial findings identified important SQ metrics as sharpness, tonality, and fluctuation strength. This document is a supplement to the initial findings in which the following are discussed: (i) a detailed treatment of the sound generation process, (ii) the impact of analyzing results with stimuli measured in the EER instead of the intended synthesized stimuli, (iii) an evaluation of annoyance responses with certification metrics, and (iv) adjunct analyses related to the test methodology.

Psychoacoustic test, psychoacoustics, sound qualit↗