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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

Multi-Image Registration for an Enhanced Vision System

An Enhanced Vision System (EVS) utilizing multi-sensor image fusion is currently under development at the NASA Langley Research Center. The EVS will provide enhanced images of the flight environment to assist pilots in poor visibility conditions. Multi-spectral images obtained from a short wave infrared (SWIR), a long wave infrared (LWIR), and a color visible band CCD camera, are enhanced and fused using the Retinex algorithm. The images from the different sensors do not have a uniform data structure: the three sensors not only operate at different wavelengths, but they also have different spatial resolutions, optical fields of view (FOV), and bore-sighting inaccuracies. Thus, in order to perform image fusion, the images must first be co-registered. Image registration is the task of aligning images taken at different times, from different sensors, or from different viewpoints, so that all corresponding points in the images match. In this paper, we present two methods for registering multiple multi-spectral images. The first method performs registration using sensor specifications to match the FOVs and resolutions directly through image resampling. In the second method, registration is obtained through geometric correction based on a spatial transformation defined by user selected control points and regression analysis.

Hines, Glenn↗
NASA NTRS1994

The beetle Tribolium castaneum has a fushi tarazu homolog expressed in stripes during segmentation

The genetic control of embryonic organization is far better understood for the fruit fly Drosophila melanogaster than for any other metazoan. A gene hierarchy acts during oogenesis and embryogenesis to regulate the establishment of segmentation along the anterior-posterior axis, and homeotic selector genes define developmental commitments within each parasegmental unit delineated. One of the most intensively studied Drosophila segmentation genes is fushi tarazu (ftz), a pair-rule gene expressed in stripes that is important for the establishment of the parasegmental boundaries. Although ftz is flanked by homeotic selector genes conserved throughout the metazoa, there is no evidence that it was part of the ancestral homeotic complex, and it has been unclear when the gene arose and acquired a role in segmentation. We show here that the beetle Tribolium castaneum has a ftz homolog located in its Homeotic complex and expressed in a pair-rule fashion, albeit in a register differing from that of the fly gene. These and other observations demonstrate that a ftz gene preexisted the radiation of holometabolous insects and suggest that it has a role in beetle embryogenesis which differs somewhat from that described in flies.

NASA Discipline Developmental Biology↗
NASA NTRS2007

Entry Attitude Controller for the Mars Science Laboratory

This paper describes the preliminary concept for the RCS 3-axis attitude controller for the exo-atmospheric and guided entry phases of the Mars Science Laboratory Entry, Descend and Landing. The entry controller is formulated as three independent channels in the control frame, which is nominally aligned with the stability frame. Each channel has a feedfoward and a feedback. The feedforward path enables fast response to large bank commands. The feedback path stabilizes the vehicle angle of attack and sideslip around its trim position, and tracks bank commands. The feedback path has a PD/D structure with deadbands that minimizes fuel usage. The performance of this design is demonstrated via simulation.

Mars↗
DOE OSTI2024

Options for Achieving Cost Reduction in Advanced Reactors through Open Architecture

A key contributor to high capital costs and schedule overruns for new nuclear power plants is lack of standardization, driven by site-specific customization and construction of multiple designs by competing vendors rather than commitment to a single standardized program. While advanced reactor vendors typically individually target repeat construction of standardized units, the many competing designs could exacerbate the problem. “Open Architecture”, the open specification of requirements and interfaces for structures, systems and components (SSCs), has been proposed as a means of promoting standardization, by facilitating existing non-nuclear suppliers to enter the industry and/or allowing SSCs to be configured for more than one reactor within the same technology type. Contracting mechanisms that facilitate information sharing and alignment of incentives between stakeholders may complement such an approach. A preliminary scheme is presented for selection of SSCs for which such strategies could be adopted, based on a vendor make/buy decision model and stakeholder interviews. SSCs are categorized according to number of suppliers and their contribution to the reactor’s competitive edge. SSCs with many potential suppliers and a high contribution to competitive edge may be attractive for widening the supply chain via open specification of system requirements and interfaces, e.g., SSCs in the power island. SSCs with few suppliers and low contribution to competitive edge may be potential avenues for common system specification between vendors, e.g., some of the auxiliary SSCs. Potential cost reductions from such strategies will depend upon the size of the build program and the reactor type.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

20%-efficient polycrystalline Cd(Se,Te) thin-film solar cells with compositional gradient near the front junction

Bandgap gradient is a proven approach for improving the open-circuit voltages (V OC s) in Cu(In,Ga)Se 2 and Cu(Zn,Sn)Se 2 thin-film solar cells, but has not been realized in Cd(Se,Te) thin-film solar cells, a leading thin-film solar cell technology in the photovoltaic market. Here, we demonstrate the realization of a bandgap gradient in Cd(Se,Te) thin-film solar cells by introducing a Cd(O,S,Se,Te) region with the same crystal structure of the absorber near the front junction. The formation of such a region is enabled by incorporating oxygenated CdS and CdSe layers. We show that the introduction of the bandgap gradient reduces the hole density in the front junction region and introduces a small spike in the band alignment between this and the absorber regions, effectively suppressing the nonradiative recombination therein and leading to improved VOCs in Cd(Se,Te) solar cells using commercial SnO 2 buffers. A champion device achieves an efficiency of 20.03% with a V OC of 0.863 V.

14 SOLAR ENERGY↗
DOE OSTI2021

Interplay between charge ordering and geometric ferroelectricity in LuFe 2 O 4 /LuFeO 3 superlattices

Oxide superlattices have drawn great attentions owing to the intriguing coupling among elastic, electrical, and magnetic orderings at the interfaces and the emerging of improper ferroelectricity. Here, superlattices composed of hexagonal LuFeO 3 (h-LuFeO 3 ) and LuFe 2 O 4 are investigated via density functional theory calculations. h-LuFeO 3 is a well-known multiferroic material that is stable only in thin-film or doped bulk state, while LuFe 2 O 4 is a charge ordered material where the existence of ferroelectricity is still in controversy. We have found that the charge ordering (CO) induced polarizations in LuFe 2 O 4 layers coexist with the geometric polarizations in h-LuFeO 3 layers in the (LuFe 2 O 4 ) m /(LuFeO 3 ) n superlattices with different periodicities, and the ferroelectric states are generally preferred over the antiferroelectric states for LuFe 2 O 4 in superlattices. The out-of-plane polarizations in h-LuFeO 3 and LuFe 2 O 4 layers tend to be aligned in parallel, and the overall polarization increases with the ratio of h-LuFeO 3 . The influence of layered polarizations on the local electrostatic potential is not significant except the detected small trend caused by the CO-induced polarization within a FeO bilayer. Besides, the local electronic structures show that the Fermi level position in a certain layer can be tuned by the valences of Fe in this layer and the polarization distributions in neighboring layers. LuFe 2 O 4 layers sandwiched between thick h-LuFeO 3 layers are more susceptible. The calculated configurations of the superlattices are supported by atomic-resolution transmission electron microscopy experiments. Our results pave a way for tunable ferroelectricity in superlattice systems and create a new playground for manipulating the coupling between various degrees of freedom.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Demonstration of p-side down green light emitting diodes with high external quantum efficiencies

GaN/(In,Ga)N heterostructure based visible Light Emitting Diodes (LED) have enabled a wide range of solid-state lighting applications through excellent efficiency and power output in the shorter wavelengths (≤ 475nm) of violet/blue emission. However, the efficiency of emitters in the longer wavelength range (≥ 500nm) drops drastically due to the need to include higher Indium-content in the InGaN quantum wells. Large average polarization fields for high Indium-content quantum wells for conventional P-up structure, opposes the depletion field leading to large electrostatic barriers for both electrons and holes injection. LEDs fabricated along the N-polar direction with a p-up orientation or Ga-polar direction with p-down orientation lower such electrostatic barriers to carrier injection due to alignment of the polarization dipole field and depletion region field. This can therefore theoretically improve the electrical injection efficiency and reduce the forward voltage of operation. Such a Ga-polar p-down LED requires a bottom buried tunnel junction to avoid current spreading issues for a buried p-GaN layer. In this report, we demonstrate for the first time Ga-polar p-down green emitting LEDs using bottom tunnel junctions and having external quantum efficiencies comparable to those of equivalent p-up LEDs grown by Metal Organic Chemical Vapor Deposition (MOCVD).

36 MATERIALS SCIENCE↗
DOE OSTI2024

Spin Effects in Low Dimensional Correlated Systems (Final Technical Report)

Our program focuses on the behavior of two-dimensional superconducting systems that have been placed in high magnetic fields and/or in contact with magnetic materials. Our specific research agenda is organized into two separate but related areas. The first is a study of disorder and correlation effects in extremely thin superconducting aluminum, beryllium, and rhenium films that have been subjected to very high magnetic fields. We are particularly interested in understanding how the coupling between the applied field and the electron spins affects the system’s ability to form superconducting state. We now have good evidence that as the electron spins in these superconductors attempt to align to the magnetic field, a new superconducting phase emerges near the critical field transition and that this phase has a significant influence on the character of the transition. Thus, the spin behavior near the transition is much more complex than expected. The second class of systems is proximity structures comprised of superconducting/ferromagnetic (SC/FM) and superconducting/heavy metal (SC/HM) bilayers. We have developed spin-resolved tunneling probes that give us a direct measure of the proximity-induced exchange field in the SC/FM structures, as well as the spin-orbit scattering rate in SC/HM structures. Recently we have demonstrated that the magnitude of the exchange field can be modulated with an external gate, thereby producing a magneto-electric response in the bilayers. We plan to optimize this magneto-electric effect by getting a better understanding of the microscopic mechanism of the interface-induce exchange field, as well as improving the gate barriers and/or the bilayer interface quality. The ultimate goal is to develop a device such as a voltage-controlled superconducting switch or a spin- polarized electron source with a voltage-tunable Zeeman splitting.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Microstructure and Mechanical Properties of Scaled Thermally Aged LPBF 316H SS Builds

As part of the US Department of Energy’s Advanced Materials and Manufacturing Technologies program’s mission to accelerate qualification of advanced manufacturing pathways for nuclear applications, laser powder bed fusion (LPBF) 316H stainless steel (SS) has been selected as a model system to develop a rapid code case framework. This effort directly addresses the grand challenges of (1) expanding the limited portfolio of materials currently codified for elevated-temperature nuclear structural service under Section III, Division 5 of the American Society of Mechanical Engineers’ Boiler and Pressure Vessel Code; and (2) significantly reducing qualification timelines that traditionally exceed a decade. The strategic importance of LPBF 316H lies in its immediate industrial relevance, existing data foundation from wrought 316H, and alignment with ongoing code case development for LPBF 316L. Prior work revealed accelerated precipitation of deleterious secondary phases and reduced creep ductility in as-printed LPBF 316H. Building on that prior research, FY 2025 activities focused on establishing an understanding of the key failure mechanisms of crept 316H specimens to aid in code case development and on evaluating stress relief (SR) parameters on the high-temperature performance and thermal aging induced degradation of tensile and fracture behavior in LPBF 316H.

36 MATERIALS SCIENCE↗
NASA NTRS1978

Rocket ultraviolet imagery of the Andromeda galaxy

Far-UV electrographic imagery of M31 is presented which was obtained during a sounding-rocket flight with an electrographic Schmidt camera sensitive in the wavelength range from 1230 to 2000 A. The resolution in the imagery is such that 50% of the energy from a point source is confined within a circle 40 arcsec in radius. Two conspicuous features are observed in the UV image of M31: one corresponding to a bright association (NGC 206) in the SW region of the disk and one centered on the galactic nucleus. Indications of the general spiral-arm structure are also evident. Absolute photometry and brightness distributions are obtained for the observed features, and both the central region and NGC 206 are shown to be diffuse sources. It is found that the brightness distribution of the central region is a flat ellipse with its major axis closely aligned with the major axis of the galaxy, which favors a source model consisting of young early-type stars close to the galactic plane and constitutes strong evidence against a nonthermal point source at the galactic center.

Carruthers, G. R.↗
NASA NTRS1985

Moisture loss from graphite structures for the Hubble Space Telescope

The construction and telescope assembly of the NASA's Hubble Space Telescope (HST) is described with particular reference to the features of its construction material. Due to the hygroscopic nature of the graphite-fiber reinforced epoxy, used for much of the structure of the HST, the telescope, when in orbit, suffers losses of water, absorbed during on-ground procedures, accompanied by shrinkage of the epoxy matrix, and needs periodic realignment. Using a combination of analytic, laboratory measured, and in-space measured data, an operational plan for adjusting the alignment of the HST is presented. The refocusing plan must take into account the preceding ground environment, as well as the prelaunch, lift-off, and predeployment environments of the HST-bearing Space Shuttle.

Facey, T. A.↗
NASA NTRS2024

Exploring Standing and Reflected Slow-mode Waves in Flaring Coronal Loops: A Parametric Study Using 2.5D MHD Modeling

Abstract Recent observations of reflected propagating and standing slow-mode waves in hot flaring coronal loops have spurred our investigation into their underlying excitation and damping mechanisms. To understand these processes, we conduct 2.5D magnetohydrodynamic (MHD) simulations using an arcade active region model that includes a hot and dense loop. Our simulations allow for in-depth parametric investigations complementing and expanding our previous 3D MHD modeling results. We excite these waves using a large-amplitude, flow pulse applied at one footpoint of the loop in two distinct models as motivated by observations from the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA). The first model (Model 1) incorporates classical compressive viscosity coefficient, while the second model (Model 2) adopts a 10-times enhanced viscosity coefficient. We obtain the following major results: (1) Our 2.5D MHD simulations reinforce previous conclusions derived from 1D and 3D MHD models that significantly enhanced viscosity is crucial for the rapid excitation of standing slow waves with damping times consistent with observations by Wang et al. (2015). (2)We uncover that nonlinearity in Model 1 delays the conversion of a reflected propagating wave into a standing wave. In contrast, Model 2 exhibits a much weak influence of nonlinearity on the excitation time of standing waves, thanks to the suppression of these effects by enhanced viscosity. (3) Our results reveal that the transverse temperature structure holds more influence on wave behavior than the density structure. In Model 1, increased loop temperature contrast significantly enhances wave trapping within the structure, mitigating the impact of temperature-dependent viscous damping. Conversely, in Model 2, the impact of temperature structure on wave behavior weakens in comparison to the effect of viscosity. (4) Model 1 displays evident nonlinear coupling to the fast and kink magnetoacoustic waves and pronounced wave leakage into the corona. Model 2 exhibits significantly weaker effects in this regard. Analyzing three observed wave events by SDO/AIA aligns with Model 2 predictions, providing further support for the substantial viscosity increase. Our 2.5D study unravels the complex interplay of wave-flow phenomena and nonlinear processes in coronal loops, extending our previous 1D modeling results to incorporate more realistic loop geometry. This provides insights into scenarios where 3D effects may be neglected, thereby enhancing our understanding of the intricate dynamics of the solar corona.

Tongjiang Wang↗
DOE OSTI2021

Three-dimensional atomic scale characterization of {11$\overline{2}$2} twin boundaries in titanium

The {11$\overline{2}$2}<11$\overline{23}$> compression twin can accommodate a considerable amount of strain under c-axis compression in Ti. However, unlike the tensile twin, the structure of the {10$\overline{1}$2}$\langle$$\overline{1}$011$\rangle$ compressive twins has not been completely characterized. In this study, we apply a combined technique of HR-TEM characterization, topological analysis, and atomistic simulations to explore the facets that bound the {11$\overline{2}$2}<11$\overline{23}$> twin in Ti. In addition to the currently known facets (CTB and B-Py), six new facets are observed and categorized for the first time from atomic-scale TEM observations along five crystallographic directions. The six new facets are (11$\overline{2}$0)//(11$\overline{2}$6), PrPr1, PyPy1, (2$\overline{11}$1)//($\overline{1}$2$\overline{1}$2), (1$\overline{1}$04)//(01$\overline{11}$), and (01$\overline{1}$0)//(2$\overline{11}$4). Results from the topological and computational analysis are in reasonable agreement with and support the HRTEM observations. Specifically, (1) the observed facets align with low-index interfaces in both twin and matrix domains, (2) the facets with lower surface energies are found to form extended interfaces, and (3) high-surface-energy facets are found at the twin tip region and explained by the fact that the energy of the combined facet and facet junction configuration is energetically preferred in the twin tip region. These results not only provide a comprehensive understanding of the 3D structure of the {11$\overline{2}$2}<11$\overline{23}$> compressive twins in Ti, but also validate the MD procedure and the Ti interatomic potential employed. This is extremely important for future study of the {11$\overline{2}$2} twin mobility and interactions with other defects, both features that remain extremely challenging to capture in experiments.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Extending Interfaces in 3D to Achieve Superior Nanoscale Strength in Ti/Nb Nanolaminates

Tuning the atomic-level structure of nanolaminates enables high strength, increased deformability, and the ability to absorb and mitigate damage due to varied crystalline defects, including dislocations. Here, we present the enhanced strength of Ti/Nb nanolaminates containing thick 3D interfaces (3DIs), relative to their chemically abrupt 2D counterparts. We examine the effects of crystallographic alignment and compositional gradients on mechanical behavior via experiments and phase-field-dislocation dynamics (PFDD) modeling. Mechanical testing reveals that nanolaminates containing thicker 3DIs demonstrate a 28% hardness enhancement compared with sharp-interface nanolaminates. PFDD modeling shows that the critical resolved shear stress (CRSS) increases with the 3DI thickness. Gradual compositional transitions in 3DIs were confirmed via scanning transmission electron microscopy and high-resolution transmission electron microscopy, showing sharp crystallographic transitions and a heightened interface topography. The findings establish a positive function between the 3DI thickness and mechanical robustness for hexagonal-closest-packed-containing composites, emphasizing the role of defect–interface interactions in tailoring the mechanical performance and providing a foundation for future interfacial engineering.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Lightning Interferometry Uncertainty, Beam Steering Interferometry, and Evidence of Lightning Being Ignited by a Cosmic Ray Shower

Abstract We present an uncertainty analysis on correlation‐based time delay estimate, the basis for broadband lightning interferometry. A normal interferometry would yield much higher uncertainties than the theoretically predicted lower bound due to finite correlation window lengths. However, if the signals are aligned in time, the uncertainties approach the lower bound and can be used to indicate the interferometric uncertainties. Based on this, we introduce a beam steering interferometry technique. It first estimates a direction centroid for the lightning sources with a normal interferometry and computes the time delays among the signals. It then shifts the raw data with the time delays to align the signals roughly in time and reprocess the aligned signals. It finally pushes the reprocessed results to their correct positions, based on the time delays estimated in the first step. We apply this technique on a fast positive breakdown (FPB) process that started a normal intracloud lightning. The FPB process is shown to have a much more complex structure and development than a normal interferometry would provide. More importantly, from both interferometric and polarization analyses, the FPB appears to be ignited by a cosmic ray shower (CRS). We estimate the radio frequency strength and frequency content related to a presumed CRS in a thunderstorm electric field and find that they are in agreement with the observations. We examine the electric field effect of the CRS front and find that it could raise the field above the threshold for positive breakdown and is capable of igniting the FPB (and the lightning).

Shao, Xuan‐Min↗
DOE OSTI2025

Causal Directions Matter: How Environmental Factors Drive Convective Cloud Detrainment Heights

This study investigates how environmental factors influence the level of maximum detrainment (LMD) in deep convective clouds. Through a novel application of the Linear Non‐Gaussian Acyclic Model (LiNGAM), we discover causal structures between environmental variables and LMD, observed at six tropical sites operated by the Atmospheric Radiation Measurement (ARM) user facility. LiNGAM effectively identifies causal directions among variables of interest, revealing robust relationships such as those among the lifting condensation level (LCL), level of free convection (LFC), and convective inhibition (CIN), aligning with prior knowledge. Relative humidity is shown to directly influence LMD; however, this relationship exhibits strong nonlinearity and becomes difficult to detect when the contrast between oceanic and continental environments is excluded from the analysis. This study highlights the importance of establishing causal relationships before performing statistical inference.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Ubiquity of amplitude-modulated magnetic ordering in the H - T phase diagram of the frustrated non-Fermi-liquid YbAgGe

YbAgGe contains a magnetic geometrically frustrated kagome-like lattice that also features significant local single-ion anisotropy. The electronic state is established by hybridization of 4f and conduction electrons leading to heavy electronic masses. The competition between these various interactions leads to nontrivial behavior under external magnetic field, including a sequence of magnetic phase transitions, non-Fermi-liquid states, and possibly a quantum critical point. We present a series of neutron diffraction experiments performed in the mK temperature range and under magnetic fields up to 8 T in the hexagonal plane, revealing the microscopic nature of the first four subsequent magnetic states of this phase diagram. The magnetic phases are associated with the propagation vectors K 1 =($\frac{1}{3}$ 0 $\frac{1}{3}$) for H < 2 T, K 2 = (0 0 0.32) for 2 T < H < 3 T, K 1 = ($\frac{1}{3}$ 0 $\frac{1}{3}$) for 3 T < H < 4.5 T and k 3 = (0.195 0.195 0.38) for 4.5 T < H < 7 T. Our structural refinements reveal a strong modulation of the magnetic moment amplitude in all phases. We observe that the ordered moments of the three magnetically different Yb sites become increasingly different in field, which complies with the principle local anisotropy directions relative to the field direction. While the ordered moments are aligned predominantly in the hexagonal plane, we also find a significant out-of-plane component and a ferromagnetic contribution above 2 T. Here we discuss possible scenarios that may evolve around the phase boundary at 4.5 T, which is associated with putative quantum criticality as identified by various bulk probes. We propose further steps that are required to better understand the microscopic interactions in this material.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Autonomous alignment and healing in multilayer soft electronics using immiscible dynamic polymers

Self-healing soft electronic and robotic devices can, like human skin, recover autonomously from damage. While current devices use a single type of dynamic polymer for all functional layers to ensure strong interlayer adhesion, this approach requires manual layer alignment. In this study, we used two dynamic polymers, which have immiscible backbones but identical dynamic bonds, to maintain interlayer adhesion while enabling autonomous realignment during healing. These dynamic polymers exhibit a weakly interpenetrating and adhesive interface, whose width is tunable. When multilayered polymer films are misaligned after damage, these structures autonomously realign during healing to minimize interfacial free energy. Finally, we fabricated devices with conductive, dielectric, and magnetic particles that functionally heal after damage, enabling thin-film pressure sensors, magnetically assembled soft robots, and underwater circuit assembly.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗