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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

pyRMG: A framework for high-throughput, large-cell DFT calculations on supercomputers

Exascale computing delivers the raw power to simulate ever larger and more chemically realistic systems, but realizing this potential requires codes that can efficiently use thousands of processors. Our real-space multigrid (RMG) density functional theory (DFT) code’s grid-decomposition approach scales nearly linearly with the number of graphics processing units (GPUs), even for simulations exceeding thousands of atoms. This scalability makes RMG a compelling tool for high-throughput DFT studies of materials that would otherwise be bottlenecked in other codes (for example, by global fast Fourier transforms in plane-wave DFT). However, the limited workflow infrastructure for RMG has thus far constrained its adoption to a small user community. In this work, we present pyRMG, a Python package designed to streamline the setup and execution of RMG DFT calculations. Built on the pymatgen and ASE (Atomic Simulation Environment) computational materials science Python packages, pyRMG automates input generation and convergence checking, and it integrates with modern job schedulers (e.g., Flux) on leadership-class platforms such as Frontier and Perlmutter. Here, we demonstrate pyRMG for a high-throughput study of strain effects in 2D 2L-Bi 2 Se 3 /2L-NbSe 2 heterostructures, which offers chemical insights into this system and shows that RMG-based workflows can converge with limited user intervention.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Single-shot ultrafast dynamics of nanosecond pulsed plasmas: Transition from ps–ns nonequilibrium to near-full ionization

The ultrafast multi-stage evolution of state-defining properties in atmospheric-pressure nanosecond pulsed plasmas is quantified using single-discharge, jitter-free, continuous streak-sweep spectroscopy of N 2 (C → B) molecular and N + /O + ionic species with a single-shot time resolution as short as ∼160 ps. An early period of extreme nonequilibrium is observed with vibrational temperatures [T V (C)] dropping from ∼8000 K at <200 ps after plasma breakdown to <4000 K within ∼1 ns, with near-ambient rotational temperatures [T R (C)] ∼ 300 K due to limited collisional energy transfer. This early-time T V (C) trend is representative of a direct and unquenched look into the high-energy tail of the electron energy distribution function; thus, it tracks real-time changes in the mean electron energy via the N2(C) emission signatures. This is followed by the rapid onset of N + /O + ionic emission after a distinct time delay of ∼14.9 ns due to multistep chemical kinetics. The ionic emission enables determination of electron densities (n e ) >2 × 10 19 cm −3 and electron temperatures (T e ) >36 000 K, indicating the transition to a nearly fully ionized regime. The ps–ns temporal dynamics are also compared between air and N 2 plasmas to assess the influence of collisional partners, as well as across the anode, cathode, and central gap regions to identify spatial variations in plasma behavior. Finally, this work demonstrates versatile continuously probing approach capable of spectro-temporal and spatially resolved single-shot measurements of key state variables in the ps–ns evolution of atmospheric-pressure nanosecond pulsed plasmas.

Electric discharges↗
DOE OSTI2025

Anisotropic light-tailored RKKY interaction in two-dimensional 𝑑-wave altermagnets

Altermagnets are known in spintronics for their intrinsic spin-splitting and unconventional magnetic responses, particularly to magnetic impurities. However, effectively controlling the magnetic exchange interactions in altermagnets is challenging for practical applications. Here, in this work, we propose using circularly polarized light to tune the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction in two-dimensional 𝑑-wave altermagnets. Using the real-space retarded Green's functions approach, our results show that while the Heisenberg and Ising exchanges dominate, a notable Dzyaloshinskii–Moriya (DM) interaction also plays a key role. Furthermore, the inherent strength of altermagnetism imprints chirp-like signatures into the magnetic responses, which can be dynamically tuned via light. We mainly demonstrate that gate-induced Rashba spin-orbit coupling is essential in response to light—light selectively and anisotropically adjusts the DM interaction without affecting the other exchanges. Our findings further indicate that rotating the altermagnet by 45° relative to the light's polarization direction generates a Dirac-like dispersion and different DM interactions. We finally extract critical thresholds where light reverses DM interactions along one axis or balances both in-plane components. The anisotropic light-driven control of RKKY interactions in altermagnets not only highlights their unique properties but also opens new avenues for engineering tailored magnetic characteristics in spintronic applications.

altermagnetism↗
DOE OSTI2020

Wannier representation of Floquet topological states

A universal feature of topological insulators is that they cannot be adiabatically connected to an atomic limit, where individual lattice sites are completely decoupled. This property is intimately related to a topological obstruction to constructing a localized Wannier function from Bloch states of an insulator. In this work, we generalize this characterization of topological phases toward periodically driven systems. We show that nontrivial connectivity of hybrid Wannier centers in momentum space and time can characterize various types of topology in periodically driven systems, which include Floquet topological insulators, anomalous Floquet topological insulators with micromotion-induced boundary states, and gapless Floquet states realized with topological Floquet operators. In particular, nontrivial time dependence of hybrid Wannier centers indicates impossibility of continuous deformation of a driven system into an undriven insulator, and a topological Floquet operator implies an obstruction to constructing a generalized Wannier function which is localized in real and frequency spaces. Our results pave a way to a unified understanding of topological states in periodically driven systems as a topological obstruction in Floquet states.

36 MATERIALS SCIENCE↗
DOE OSTI2020

CPAP Ventilators Needed for Rapid Response to COVID-19 by Modification of CPAP Equipment

Early on in the COVID-19 pandemic, potential ventilator shortages were a critical issue identified by national health care providers. Capacity modeling at the time suggested patient demand may exceed ventilator supply. Thus, the challenge became finding an urgent interim solution to meet health care needs. Our initial hypothesis was that CPAP technology could be modified to provide similar functionality to a ventilator, relieving demand and allowing physicians to decide which patients need high end machines, ultimately saving lives. In conjunction with medical experts and pulmonologists, we were able to identify three key thrusts associated with this research problem: (1) modification of CPAP technology to allow for 02 input that would be capable of providing ventilation; (2) development of an alarming function that would provide real-time audible alarms to alert medical personnel to critical conditions, which would be used inline with CPAP technology; and (3) a method of sterilizing expiratory air from such a system in order to protect medical personnel from biohazard, since CPAPs vent to the atmosphere. We were unable to realize results for thrust 1 (CPAP modification for 02); we identified potential safety issues associated with utilizing medical grade oxygen with a common CPAP device. In order to characterize and mitigate these issues, we would need to partner closely with a device manufacturer; such a partnership could not be achieved in the timeframe needed for this rapid response work. However, we determined that some medical grade BiPAP devices do not need this modification and that the significant progress on thrusts 2 and 3 would be sufficient to buy down risk of a massive ventilator shortage. Our team built a prototype alarm system that can be utilized with any assistive respiratory device to alert on all key conditions identified by medical personnel (high pressure, low pressure, apnea, loss of power, low battery). Finally, our team made significant progress in the rapid prototyping and demonstration of an inline UV air purifier device. The device is cost efficient and can be manufactured at scale with both commercially available and additively manufactured parts. Initial tests with SARS-CoV-2 analog bacteriophage MS2 show 99% efficacy at reducing bioburden. Following a successful demonstration of the prototype device with medical personnel, we were able to obtain follow-on (non-LDRD) funding to provide additional device characterization, validation, and production in order to respond to an immediate regional need.

42 ENGINEERING↗
DOE OSTI2026

PopGNN: Graph Neural Network-Based Flexible Future Population Forecasting Model

Accurate population forecasts is important to plan critical infrastructure and services, from housing and education to healthcare and transport. However, traditional population prediction studies have only employed traditional machine learning models limited to capture complex spatial interdependencies and patterns. Althogh recently computer vision-based framework was introduced with with promising accuracy, it has critical limitations for real-world planning applications: it function only at fixed spatial resolutions, restricting their use in diverse boundaries such as census tracts, neighborhoods, or administrative zones. Therefore, this study suggests a Graph Neural Network (GNN)-based population prediction framework, called PopGNN. This model recorded remarkable performance compared with state-of-the-art models and traditional baseline models in the grid and administrative boundaries. Furthermore, our framework achieved comparable predictive accuracy to a computer vision-based model in both the South Korea and Tennessee case studies. Consequently, this study is valuable in that a single model can provide accurate population forecasts that address diverse planning demands, ranging from granular grid-level estimates for precise service allocation and facility location planning to aggregate administrative-level forecasts for macro-scale regional policy and resource distribution.

97 MATHEMATICS AND COMPUTING↗
NASA NTRS1968

High speed correlator.

Computational procedure and circuitry of correlator for real time computation of correlation function of signals at 30 points simultaneously

Hooper, E. B., Jr.↗
NASA NTRS1969

A simple gigacycle correlator

Gigacycle correlator involving sampling oscilloscopes for real time display of correlation functions over adjustable time interval, discussing design and performance

Alexeff, I.↗
NASA NTRS1972

An operational data compression system using minicomputers.

Functional description of the real-time programmable data compression system that has been developed for operation between the data acquisition and satellite service ground stations and the ATS 1 and 3 satellites. The source data consist of TV pictures from these satellites that are received, compressed, transmitted, and reconstructed in real-time. General purpose minicomputers and specially designed I/O channels are used for compression and reconstruction. The installed compression system has passed all system input-output tests. Because of the great flexibility of the minicomputers, it is possible to vary the compression and to perform auxiliary tasks, such as data formatting.

Davisson, L. D.↗
NASA NTRS1977

MIUS Integration and Subsystem Test (MIST) data system

A data system for use in testing integrated subsystems of a modular integrated utility system (MIUS) is presented. The MIUS integration and subsystem test (MIST) data system is reviewed from its conception through its checkout and operation as the controlling portion of the MIST facility. The MIST data system provides a real time monitoring and control function that allows for complete evaluation of the performance of the mechanical and electrical subsystems, as well as controls the operation of the various components of the system. In addition to the aforementioned capabilities, the MIST data system provides computerized control of test operations such that minimum manpower is necessary to set up, operate, and shut down subsystems during test periods.

Pringle, L. M.↗
NASA NTRS1978

Forwardscattering corrections for optical extinction measurements in aerosol media. I - Monodispersions

A parametric investigation of forwardscattering corrections applicable to experimentally determined optical extinction coefficients in homogeneous aerosol media is discussed for the case of monodispersion. Assuming forwardscattering to be a single-scattering phenomenon, corrections are made by two methods: one employing the exact Mie theory, the other employing the approximate Rayleigh diffraction formula. The corrections are evaluated as functions of particle size, the real and imaginary parts of the complex refractive index, and the half-angle of the detector view cone.

Deepak, A.↗
NASA NTRS1983

Information display and interaction in real-time environments

The available information bandwidth as a funcion of system's complexity and time constraints in a real time control environment were examined. Modern interactive graphics techniques provide very high bandwidth data displays. In real time control environments, effective information interaction rates are a function not only of machine data technologies but of human information processing capabilities and the four dimensional resolution of available interaction techniques. The available information bandwidth as a function of system's complexity and time constraints in a real time control environment were examined.

Bocast, A. K.↗
NASA NTRS1987

Command and control of the Voyager spacecraft

The Voyager Mission was designed to be conducted using reprogrammable onboard computers. This decision was based on the need for highly reliable semi-autonomous operations of the spacecraft and the lengthy two-way communication times envisioned during the mission. Command and control of the spacecraft is effected by the process through which the programs for these computers are developed. While this results in a relatively passive real-time command and control function, provisions exist for intervention to occur in order to modify or augment the programs or respond to spacecraft anomalies.

Adamski, Terrence P.↗
NASA NTRS1989

On the Gortler vortex instability mechanism at hypersonic speeds

The linear instability of the hypersonic boundary layer on a curved wall is considered. As a starting point the viscosity of the fluid is taken to be a linear function of temperature and real-gas effects are ignored. It is shown that the flow is susceptible to Gortler vortices and that they are trapped in the logarithmically thin adjustment layer in which the temperature of the basic flow changes rapidly to its free stream value. The vortices decay exponentially in both directions away from this layer and are most unstable when their wavelength is comparable with the depth of the adjustment layer. The non-uniqueness of the neutral stability curve associated with incompressible Gortler vortices is shown to disappear at high Mach numbers if the appropriate fast streamwise dependence of the instability is built into the disturbance flow structure. It is shown that in the hypersonic limit wall-cooling has a negligible effect on the stability of a fluid with a given value of the Chapman constant.

Hall, Philip↗
NASA NTRS1990

Theoretical investigation of gas-surface interactions

A Dirac-Hartree-Fock code was developed for polyatomic molecules. The program uses integrals over symmetry-adapted real spherical harmonic Gaussian basis functions generated by a modification of the MOLECULE integrals program. A single Gaussian function is used for the nuclear charge distribution, to ensure proper boundary conditions at the nuclei. The Gaussian primitive functions are chosen to satisfy the kinetic balance condition. However, contracted functions which do not necessarily satisfy this condition may be used. The Fock matrix is constructed in the scalar basis and transformed to a jj-coupled 2-spinor basis before diagonalization. The program was tested against numerical results for atoms with a Gaussian nucleus and diatomic molecules with point nuclei. The energies converge on the numerical values as the basis set size is increased. Full use of molecular symmetry (restricted to D sub 2h and subgroups) is yet to be implemented.

Dyall, Kenneth G.↗
NASA NTRS1989

On the Goertler vortex instability mechanism at hypersonic speeds

The linear instability of the hypersonic boundary layer on a curved wall is considered. As a starting point, the viscosity of the fluid is taken to be a linear function of temperature and real-gas effects are ignored. It is shown that the flow is susceptible to Goertler vortices and that they are trapped in the logarithmically thin adjustment layer in which the temperature of the basic flow changes rapidly to its free stream value. The vortices decay exponentially in both directions away from this layer and are most unstable when their wavelength is comparable with the depth of the adjustment layer. The nonuniqueness of the neutral stability curve associated with incompressible Goertler vortices is shown to disappear at high Mach numbers if the appropriate 'fast' streamwise dependence of the instability is built into the disturbance flow structure. It is shown that in the hypersonic limit, wall-cooling affects the leading-order term in the expansion of the Goertler number which is independent of the wavenumber, and which is due to the curvature of the basic state but it has a negligible effect on the other terms which are dependent on the wavenumber.

Hall, Philip↗
NASA NTRS1990

Applying real-time operations to integrate and evaluate Space Station Freedom design

During its 30 year lifetime, Space Station Freedom will provide unique opportunities for a variety of research, commercial and space exploration activities. The diversity of Freedom's on-orbit operations and the partitioning of the spacecraft's flight elements and systems requires consideration of operations early in the design development. This paper presents a method for defining a structured relationship between Space Station Freedom real-time operations and system functionality, and discusses how this relationship can be used when evaluating the spacecraft design.

Schmidt, George↗