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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
NASA NTRS1998

Mesogranulation as A Distinct Scale of Convection in the Sun

We present evidence for the existence of mesogranulation as a scale of convection distinct from granulation and supergranulation through analysis of full-disk Doppler velocity images of the Sun collected by the Michelson Doppler Imager (MDI) aboard the NASA/ESA Solar and Heliospheric Observatory (SOHO). Our analysis procedures isolate nearly steady flows in the solar photosphere and yield power spectra of convection for spherical harmonic degrees up to I = 1000. Each spectrum exhibits an obvious supergranulation peak at I approximately 130 and a broad secondary peak at I approximately 600 with a distinct break in the spectrum between these peaks at I approximately 300. We believe that this secondary peak is a signature of mesogranulation with typical cell diameters of about 7 Mm. Our standard analysis procedure is to first remove the p-mode oscillation signal by averaging individual Dopplergrams over 17-minute intervals. Next, by fitting to standard functional forms we remove Doppler signals due to the motion of the spacecraft, the convective blueshift, solar rotation including differential rotation, and the meridional circulation in order to produce Dopplergrams dominated by convective motions. By mapping these processed images onto heliographic coordinates and projecting onto spherical harmonics, we produce a power spectrum of solar convection for each 17-minute period. We construct synthetic images and pass them through the same analysis procedure in order to determine the actual solar convection spectrum that reproduces the analyzed results. We find that a small but increasing percentage of high-degree convective power is lost in the analysis as we approach the limit of resolution of the detector but'that the broad, mesogranulation peak at I approximately 600 must be included in the convection spectrum of the synthetic images.

Bachmann, Kurt T.↗
DOE OSTI2023

Integral Field Spectroscopy of the cometary starburst galaxy NGC 4861

ABSTRACT Using the PMAS Integral Field Unit on the Calar Alto 3.5 m telescope, we observed the southern component (Markarian 59) of the ‘cometary’ starburst galaxy NGC 4861. Mrk 59 is centred on a giant nebula and concentration of stars 1 kpc in diameter. Strong $\rm H\,\alpha$ emission points to a star-formation rate (SFR) at least 0.47 $\rm M_{\odot }\, yr^{-1}$. Mrk 59 has a very high [O iii] $\rm \lambda 5007/H\,\beta$ ratio, reaching 7.35 in the central nebula, with a second peak at a star-forming hotspot further north. Fast outflows are not detected but nebular motion and galaxy rotation produce relative velocities up to 40 km $\rm s^{-1}$. Spectral analysis of different regions with ‘Fitting Analysis using Differential evolution Optimization’ (FADO) finds that the stars in the central and ‘spur’ nebulae are very young, $\rm \le 125~Myr$ with a large $\rm \lt 10~Myr$ contribution. Older stars ($\rm \sim 1~Gyr$) make up the northern disk component, while the other regions show mixtures of 1 Gyr age with very young stars. This and the high specific SFR $\rm \sim 3.5~Gyr^{-1}$ imply a bimodal star formation history, with Mrk 59 formed in ongoing starbursts fuelled by a huge gas inflow, turning the galaxy into an asymmetric ‘green pea’ or blue compact dwarf. We map the He ii λ4686 emission, and identify a broad component from the central nebula, consistent with the emission of ∼300 Wolf–Rayet stars. About a third of the He ii λ4686 flux is a narrow line emitted from a more extended area covering the central and spur nebulae, and may have a different origin.

Roche, Nathan (ORCID:0000000319363058)↗
DOE OSTI2020

Winners are not keepers: Characterizing household engagement, gains, and energy patterns in demand response using machine learning in the United States

Demand-response programs can help utilities manage rapidly evolving electric grids, but these programs are subject to the complexities of human behavior. This paper explores a novel method for uncovering heterogeneity in households. In this work, we use a machine-learning method known as a Conditional Inference Tree (c-tree) algorithm to categorize households based on their energy behavior characteristics collected via smart meters, and explore how this translates through into heterogeneity in their real-world response to a DR program. Using data from randomized controlled trial, we generate estimates of the changes in energy use caused by the program within each household group. Our results show that the c-tree approach differentiates households by their energy-use characteristics in a way that increases the spread in enrollment rates and critical peak reduction among household groups, compared with the spreads achieved via several conventional segmentation methods. Thus, the c-tree analysis enables the most tailored targeting of major potential energy savers and could provide the greatest increase in cost-effectiveness of household recruitment into DR programs. Our results also offer fresh insights into the relationships between household energy behavior characteristics – such as peak energy use and “structural winningness” (the ability to save money under a DR program without changing energy-use behaviors) – and household decisions about enrolling in DR programs and reducing energy use. Our research also demonstrates the potential of smart meter data, combined with machine learning and econometric methods, to provide significant value to utilities, program implementers, researchers, and other stakeholders.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2026

Adaptively coupled phase retrieval in multi-peak Bragg coherent diffraction imaging

Recent advances in Bragg coherent diffraction imaging (BCDI) experimental techniques permit routine measurement of multiple Bragg peaks from a single crystalline grain. The resulting images contain the full lattice distortion vector field which can be differentiated to provide lattice strain and rotation. With the advent of fourth-generation synchrotron light sources, such multi-peak datasets are produced at high rates, facilitating the need for rapid phase retrieval of the multiple peaks and subsequent image analysis. Here we describe and demonstrate a new implementation of a coupled phase retrieval technique for multi-peak BCDI which simultaneously treats each Bragg peak of the dataset and produces a three-dimensional image of the crystal's morphology and lattice distortion field. In addition, this method uses the redundant information contained in the various Bragg diffraction patterns to detect and suppress spurious signal appearing on the detector in a subset of the measurements. Compared with manual data editing, adaptive coupling produces a more consistent phase profile in reciprocal space and sharper surfaces in direct space, with no significant difference in computational cost. These improvements reduce the need for manual preprocessing and enable robust high-throughput analysis of multi-peak BCDI data, supporting near-real-time strain microscopy at modern synchrotron facilities.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Portable Soft X-Ray Diagnostics for Transformative Fusion-Energy Concepts (Final Scientific/Technical Report)

A time-gated extreme-ultraviolet spectrometer was fielded on a transformative fusion-energy device, FuZE-Q at Zap Energy, Inc. (ZEI), a sheared-flow-stabilized z-pinch. Plasma emission spectra were collected in the 5–40 nm wavelength (30–250 eV) range. This was the first time a direct-vacuum-coupled, high-voltage, deposition-sensitive diagnostic was fielded on this type of dense-plasma fusion device. To overcome the special challenges of such a coupling, a unique, highly effective implementation was developed, with fast (10-ns risetime) pulsed high-voltage electronics and a multi-stage differential pumping system. This enabled the UNR spectrometer to collect three independently timed spectra per FuZE-Q shot while also protecting sensitive internal components. Analysis of line emission identified oxygen (N-, C-, B-, Be-, Li-, and He-like O), peaking in intensity shortly after maximum current (>500 kA). Spectral databases and collisional-radiative modeling have been used to identify impurities and estimate edge-plasma temperatures.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Measurement of the Triple-Differential Cross Section of Muon Neutrino Charged Current Interactions with Low Hadronic Activity in the NO$\nu$A Near Detector

This dissertation describes the analysis and measurement of the triple-differential cross-section of the $\nu_\mu CC$ interaction with Low Hadronic Activity (maximum kinetic energy of 250 MeV for protons and 175 MeV for pions) in the NOvA Near Detector. This cross-section is reported in bins of Muon Kinematics and available hadronic energy. The data corresponds to an accumulated $14.2\times10^{20}$ protons-on-target (POT) in the neutrino mode of the NuMI beam, with a narrow band of neutrino energies peaked at 1.8 GeV. The analysis provides a sample of neutrino–nucleus interactions with an enhanced fraction of quasi-elastic (QE) and two-particle-two-hole (2p2h) interactions and a suppression of resonant pion production (RES) and deep inelastic scattering (DIS) interactions. This enhancement of QE and 2p2h allows for quantitative comparisons with various models of these processes. We find strong disagreement between data and theory-based models in the forward muon direction, especially for the 0.2-0.4 GeV available hadronic energy region.

Lesmeister, James Ryan [Houston U.]↗
DOE OSTI2026

Energetic Copolymers From LLM-105 and Aliphatic Isocyanates

Energetic polymers typically feature fuel-rich backbones with pendant oxidizing explosophores, which are used to modify pressure and temperature characteristics in energetic formulations. However, these pendant explosophores generally increase sensitivity and decrease the thermal stability of the polymer in the condensed phase. Direct polymerization of insensitive high explosives (IHEs) bearing polymerizable functionalities, such as amines, provides a synthetic platform for deriving tunable energetic materials. Here, this work demonstrates the first direct polymerization of the IHE 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) with aliphatic isocyanate comonomers to yield an energetic copolyurea (PUa1) and an energetic copolyurea network (PUa2). 1 H and 13 C nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR) confirm copolyurea synthesis. PUa1 exhibited branching reactions commonly found in polyurea syntheses, and these side reactions were suppressed in PUa2 through use of a polyfunctional isocyanate. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) demonstrate the energetic IHE based polyurea preserves the energetic decomposition of the parent monomer LLM-105 in PUa1 (1203 J g −1 ) and PUa2 (687 J g −1 ), albeit with reduced thermal stability with peak decomposition temperatures of 235°C and 233°C, respectively. This work presents a new approach for generating energetic polymers from IHE cores with tunable energetic, thermal, and structural characteristics.

Chemistry↗
DOE OSTI2026

Metastable multimeric G-quadruplex 2′FY-RNA aptamers that selectively bind pyoverdines

Two 2′FY-RNA aptamers with distinct sequences were selected for specific binding to pyoverdine-Pf5 (PVD-Pf5), increasing chromophore fluorescence upon binding. They also recognized the peptide portion of pyoverdines, as shown by their differential specificity for related variants. Computational analysis and experimental data (NMM binding, CD spectra) identified G-quadruplex structures that were thermally metastable but reformed in the presence of PVD-Pf5. Further structural studies mainly with one aptamer revealed imino proton peaks in 1D H-NMR and pressure stability up to 2 kbar. Electrophoretic evidence identified dimeric G-quadruplexes formed by the 2′FY-RNA aptamers and their RNA equivalents. While cations were necessary for PVD-Pf5 binding, they were not required for G-quadruplex formation. Given the established role of G-quadruplexes as protein interaction sites, multimeric G-quadruplexes offer a potential framework for structure-based regulatory mechanisms in cellular RNAs. In addition to previously characterized multimeric G-quadruplexes, these aptamers contribute novel sequences that expand the repertoire of known multimeric G-quadruplexes.

2′FY-RNA↗
NASA NTRS1991

Comparison of numerically-simulated microphysical characteristics of convective storms with multiparameter radar observations during COHMEX

The microphysical/dynamical nature and evolution of numerically simulated convective storms observed on July 11, 1986 during the Cooperative Huntsville Meteorological Experiments are investigated with the Goddard Cumulus Ensemble model. The model-simulated hydrometeor and radar reflectivity structure is verified with results derived from the multiparameter radar observations, which includes a description of the reflectivity, differential reflectivity, linear depolarization ratio, and hail signal for two thunderstorm cases analyzed by Fulton and Heymsfield (1990). Radar analysis shows the storm to split with the newer more vigorous cell in the SE quadrant. Echo tops are near 15 km while peak reflectivities exceed 50 dBZ. Preliminary model simulations likewise show a splitting storm with regeneration occurring on the SSE flank. Echo tops are around 14 km with peak reflectivities over 45 dBZ.

Tao, W.-K.↗
DOE OSTI2023

Implementation of extreme ultraviolet spectroscopy on a sheared-flow-stabilized Z pinch

A diagnostic for extreme ultraviolet spectroscopy was fielded on the sheared-flow-stabilized (SFS) fusion Z-pinch experiment (FuZE-Q) for the first time. The spectrometer collected time-gated plasma emission spectra in the 5–40 nm wavelength (30–250 eV) range for impurity identification, radiative power studies, and for plasma temperature and density measurements. The unique implementation of the diagnostic included fast (10 ns risetime) pulsed high voltage electronics and a multi-stage differential pumping system that allowed the vacuum-coupled spectrometer to collect three independently timed spectra per FuZE-Q shot while also protecting sensitive internal components. Analysis of line emission identifies oxygen (N-, C-, B-, Be-, Li-, and He-like O), peaking in intensity shortly after maximum current (>500 kA). This work provides a foundation for future high energy spectroscopy experiments on SFS Z-pinch devices.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1987

Rotation of the coronal magnetic field

The coronal magnetic field rotates differently than the photosphere. The field configuration of the corona can be calculated from the observed photosphpere field using a potential field model. Correlation of the field patterns at different latitudes with a lag near one solar rotation shows much less differential rotation than observed in the photospheric field; however, the peak is very broad and determines the rotation rate rather poorly. Consideration of longer lags reveals a more complex rotational structure and indicates different rotation rates in the Northern and Southern Hemispheres. Spectral analysis of the equatorial dipole component of the coronal field reveals an organization into just a few discrete rotation frequencies which are apparently present simultaneously. Spectral analysis of the field at different latitudes shows that the frequencies are present simultaneously. Spectra analysis of the field at different latitudes shows that the frequencies are present simultaneously, but in different hemispheres, and that the Southern Hemisphere fields rotate more slowly than those in the north in solar cycle 21.

Hoeksema, J. T.↗
DOE OSTI2024

Metal-Catalyzed Thermo-Catalytic Decomposition and Continuous Catalyst Generation

In this study, metal dusting is utilized to initiate a two-stage thermo-catalytic decomposition (TCD) process. Stage 1 starts with metal-catalyzed TCD, and in stage 2 the metal-catalyzed carbon catalyzes additional TCD. TEM is presented of the early- versus late-stage TCD to qualitatively illustrate the second-stage TCD by the metal-catalyzed carbons. Corresponding SEM illustrates differences in growth type and surface density between early versus late reaction times, with backscattered imaging differentiating the first- versus second-stage TCD. TGA supports the microscopic inference of a second carbon phase by the presence of an early (low-temperature) reaction peak, characteristic of low-structure or disordered carbon as the second-stage TCD carbon. Raman analysis confirms that the second-stage carbon deposit is more disordered and unstructured, especially at 1000 °C, supported by the ID/IG and La value changes from 0.068 to 0.936 and 65 nm to 4.7 nm, respectively. To further confirm second-stage TCD occurrence upon pre-catalyzed carbons, two carbon blacks are tested. Exposing a combination of edge and basal or exclusively basal sites for the graphitized form, they afford a direct comparison of TCD carbon nanostructure dependence upon the initial carbon catalyst nanostructure. Pre-oxidation of the stainless-steel wool (SSW) prior to TCD is advantageous, accelerating TCD rates and increasing carbon yield relative to the nascent SSW for an equivalent reaction duration.

Chemistry↗
NASA NTRS2015

Nanoflare vs Footpoint Heating : Observational Signatures

Time lag analysis shows very long time lags between all channel pairs. Impulsive heating cannot address these long time lags. 3D Simulations of footpoint heating shows a similar pattern of time lags (magnitude and distribution) to observations. Time lags and relative peak intensities may be able to differentiate between TNE and impulsive heating solutions. Adding a high temperature channel (like XRT Be-­thin) may improve diagnostics.

corona simulation heating↗
NASA NTRSDate not supplied

Progress on Inverse Estimation Technique of Non-Linear Pitch Damping Coefficient Curves Using Free-Flight CFD Generated Trajectories

Characterization of entry vehicle pitch damping coefficient curves is crucial to ensure appropriate re-entry and overall mission success. The pitch damping coefficient (C_(m_q )+C_(m_α ̇ )) is used to encapsulate the oscillatory growth or decay of a body during a trajectory. The inverse estimation technique utilizes an existing Free-Flight CFD (FF-CFD) dataset and wraps a reconstruction algorithm in an optimizer. The reconstruction integrates the planar equations of motion derived by Schoenenberger, Queen [1] using Python’s scipy.integrate.solve_ivp. The optimizer’s objective function is the normalized 𝐿2 residual of the angle of attack peaks between the reconstructed trajectory and the original data produced with FF-CFD. Inclusion of the peak times in this residual calculation allows for simultaneous optimization of the pitch moment coefficient, C_(m_α ). This residual equation is shown below in Eq. 1. The optimizer scipy.optimize.minimize was used with the gradient-based Powell method for the analysis presented, however the differential evolution method was investigated as means of comparison, and was found to produce marginally lower residual values with prohibitively longer run times. Further, the pitch damping curve is found by fitting a cubic interpolation function to a set of (α, (C_(m_q )+C_(m_α ̇ ))) control points, where the α points are held constant and the (C_(m_q )+C_(m_α ̇ )) values are the optimized parameters. The pitch moment curve uses a linear interpolation between the minimum and maximum α in the dataset. FF-CFD generated trajectories using the Dragonfly capsule geometry with the Genesis ballistic range model parameters were simulated and used for this analysis. These FF-CFD trajectories simulate planar motion, as restricted by the reconstructing the equations of motion, of three different cases: 1-DoF (free-to-pitch), 2-DoF (free-to-pitch and heave), and 3-DoF (free-to-pitch, heave, and decelerate). Pitch damping coefficient curves generated using this inverse estimation curve technique with FF-CFD 1-DoF Dragonfly data are found in Fig. 1. Preliminary results reconstructing ballistic range shots using these FF-CFD derived predictions of the pitch damping curve (Fig. 1) are shown in Fig. 2. It should be noted that the ballistic range shot used a Genesis model whereas the FF-CFD data used a Dragonfly geometry, however these geometries are similar.

entry↗
NASA NTRS1985

Radio phase characteristics of terrain from multipolarized synthetic aperture radar data

Recent advances in digital data acquisition and signal processing technology permit simultaneous measurement of the complex (amplitude and phase) radar backscatter from several polarization-diverse antennas. While absolute phase mesurements remain to be analyzed in detail. The differential phase of signals polarized parallel and perpendicular to the plane of incidence provide information on the scattering mechanisms that dominate the interaction of the radio waves with the terrain. Analysis of phase backscatter maps from a typical urban area yields a bimodal distribution with the two peaks separated by approximately 180 degrees, highly indicative of a dominant simple geometric one bounce-two bounce mechanism. Some maps of agricultural areas exhibit a similar distribution, however, other agricultural areas yield a distribution that, while still bimodal, consists of two peaks separated by about 110 deg. Still other agricultural areas exhibit a more complex distribution. All of the observed phase shifts appear to be independent of incidence angle from at least 20 deg to 55 deg, therefore the 110 degree shifts are inconsistent with both the geometric model used for the urban area and with common dielectric slab models.

Zebker, H. A.↗
NASA NTRS2001

The Combined Detection of Morphological and Molecular Biomarkers: Implications for Astrobiology

Experience gathered by previous researchers during their hunt for evidence of early Earth life has shown the complexity in interpreting observations of possible microfossils and to establish the evidence to be positive. Similarly, the stillsimmering controversy on the nature of the nano-structures in Martian meteorite ALH84001 described by McKay et al. (1996) emphasizes the difficulties of conclusively identifying those structures as (a) fossilized bacterial cells and (b) establish their indigeneity. A better understanding of biological signatures in rocks is needed in order to identify traces of microbial life, which include morphological, mineralogical and chemical traces. It is thus considered crucial to tackle the problems emerging in the search for evidence of early life on Earth and in exopaleontological research with a multidisciplinary approach. With this is mind we applied surface sensitive Time of Flight-Secondary Ion Mass Spectroscopy (ToF-SIMS) to a previously described 25 m.y. old fossil bacterial biofilm. This technique allows in situ analysis with high mass resolution as well as molecular imaging of micron sized structures. As no extraction or derivatisation of the sample is required for ToF-SIMS analysis, electron microscopical investigation of the same samples subsequent to analysis is possible, thus allowing the combination of molecular and morphological biomarkers. The analysed fossil bacterial biofilms were associated with macrofossils from volcanoclastic lacustrine sediments from the Upper Oligocene Enspel formation (Germany). Preliminary scanning electron microscopy (SEM) studies have shown that a fossil structure interpreted as a coprolite purely consisted of fossilized bacterial biofilm. For ToF-SIMS investigation small particles were taken from the fossil biofilm and mounted onto Au-coated In-foil and analysed in a Phi Evans T-2000 TRIFT system. The ToF-SIMS analysed samples were Au/Pd-sputter coated and imaged using a Philips XL40 Field Emission Gun SEM (FEG-SEM). ToF-SIMS analysis of the organic rich fossil biofilm (TOC 29%) in the 0-100 Dalton (Da) range showed significant amounts of inorganic species, confirming the results obtained previously by EDX analysis, clearly showing the bacterial fossils to be mineralised. ToF-SIMS furthermore revealed the presence of a variety of low- and high-mass organic molecules and fragments thereof. These include peaks indicative of alkenes and alkanes, aromatic organic species and the polycyclic aromatic hydrocarbon naphthalene. More tentatively, peaks indicative of alkyl pyrroles and pyridyl-CH2 were identified. Other peaks of interest include peaks indicative of C(n)H(2n)O2 and C(n)H(2n-2)O2, which according to their general formula would suggest the presence of both saturated and unsaturated fatty acids although further in situ derivatisation experiments and GC-MS (Gas Chromatography MS) need to be applied to verify this beyond doubt. Furthermore, peaks at m/z 370, 384, 398, 412, 426, 440, 454 and 468 were identified, which indicate the potential presence of bacterial hopanes, a class of biomarkers indicative of bacteria. The main diagnostic peak for this group of chemicals is the fragment at m/z 191.18. Our studies conducted on purified hopane standards have shown that in the high-mass resolution mode differentiation of this diagnostic hopane peak and polyethylene at m/z 191.05 is possible. However, the spectra discussed here were collected in the lower resolution mapping mode, therefore this differentiation was not possible. The centroids of the possible hopane peaks obtained on the fossil biofilms are well within the range associated with bacterial hopanes. There is a strong possibility therefore that hopanoids may be associated with the fossil bacterial cells. Due to the non-destructive nature of ToF-SIMS, analysed samples can be studied using SEM, thus allowing the combination of morphological and molecular biomarkers. Subsequent SEM analysis of the ToF-SIMS analysed samples confirmed that the analysed material purely consists of fossil bacterial cells. This is thus the first successful effort to demonstrate the combination of spectral and morphological biomarkers. The advantages of highly sensitive non-destructive in situ analysis techniques for biomarker detection are invaluable, particularly with respect to envisaged Mars sample return missions, as it may allow us to identify remains and traces of former microbial life in both ancient terrestrial and extraterrestrial materials. This technique may prove particularly useful in the quest for extraterrestrial life with respect to precious extraterrestrial materials, as minute quantities are sufficient to conduct analysis.

Toporski, J.↗
DOE OSTI2026

Quaternary i-MAX Phases (Mo 2/3 RE 1/3 ) 2 AlC (RE: Dy, Tb, Er): Experimental Characterization and First-Principles Insights into their Fundamental Properties

Rare earth (RE)-based materials have unique electronic, magnetic, and optical properties, leading to the recent discovery of atomically layered solids with the chemical formula (M' 2/3 RE 1/3 ) 2 AlC, which have since garnered significant attention in the scientific community. This study aims to synthesize, characterize, and investigate the structural and thermal stability of the RE i-MAX phases. We prepared i-MAX phases using molybdenum (Mo) as M′ and RE elements as Dy, Tb, and Er, namely (Mo 2/3 Dy 1/3 ) 2 AlC, (Mo 2/3 Tb 1/3 ) 2 AlC, and (Mo 2/3 Er 1/3 ) 2 AlC. Structural characterization through x-ray diffraction (XRD) and Raman spectroscopy confirms the formation of the RE-based i-MAX phase, along with the presence of minor impurity phases in the alloys. Thermogravimetric analysis (TGA) conducted up to 1000°C under ambient conditions reveals that the i-MAX phases remain thermally stable up to approximately 450°C, beyond which oxidation leads to a noticeable weight gain in all samples. Differential scanning calorimetry (DSC) measurements during heating and cooling cycles show endothermic and exothermic peaks for (Mo 2/3 Dy 1/3 ) 2 AlC i-MAX in the 410–420°C range, indicating a temperature-induced minor atomic arrangement. In contrast, these peaks are absent in the Tb- and Er-based i-MAX phases. These findings offer valuable insights into the thermal behavior and stability of these i-MAX phases under thermal stress, contributing to a deeper understanding of their unique properties. Furthermore, first-principles density functional theory (DFT) calculations were performed to investigate the electronic and optical properties of the i-MAX phases. The results reveal their metallic nature, with pronounced contributions from Mo and RE elements near the Fermi level and within the conduction band.

Rare earth↗
NASA NTRS1974

Nonlinear panel response by a Monte Carlo approach

The vibration of clamped and simply supported elastic panels due to subsonic and supersonic turbulent boundary-layer flows is investigated by a Monte Carlo technique. The resulting generalized random forces are simulated numerically from boundary-layer turbulence spectra, and the response analysis is performed in the time domain. The mutual interaction between panel motion and external and/or internal airflow is included. Response studies are performed with respect to rms response, probability structure, peak distribution, threshold crossing and spectral density. The effect on the response statistics of in-plane loading, static pressure differential, and cavity pressure is investigated.

Vaicaitis, R.↗