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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
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Man-machine interactive imaging and data processing using high-speed digital mass storage

The role of vision in teleoperation has been recognized as an important element in the man-machine control loop. In most applications of remote manipulation, direct vision cannot be used. To overcome this handicap, the human operator's control capabilities are augmented by a television system. This medium provides a practical and useful link between workspace and the control station from which the operator perform his tasks. Human performance deteriorates when the images are degraded as a result of instrumental and transmission limitations. Image enhancement is used to bring out selected qualities in a picture to increase the perception of the observer. A general purpose digital computer, an extensive special purpose software system is used to perform an almost unlimited repertoire of processing operations.

Alsberg, H.↗
NASA NTRS1994

Modeling of the magnetosphere-ionosphere-atmosphere system

During the period covered by this report we continued to investigate basic processes in magnetosphere-ionosphere coupling and to develop algorithms for analyzing ultraviolet, visible, and X-ray images that will be acquired on the POLAR spacecraft. An image analysis procedure combines several numerical models to obtain a self-consistent picture of the ionosphere and thermosphere. Our ionosphere-aurora model was extended by the inclusion of the magnetic mirror force and a self-consistent parallel electric field in the ionosphere. The electron transport model which forms a critical part of the aurora model was evaluated by comparison with laboratory measurements and auroral observations. We determined the uncertainties that arise from our limited knowledge of cross sections and energy degradation functions for electron neutral interaction.

Source record↗
NASA NTRS2018

In-Flight Calibration of Hitomi Soft X-Ray Spectrometer. (1) Background

The X-Ray Spectrometer (XRS) instrument of Suzaku provided the first measurement of the non-X-ray background (NXB) of an X-ray calorimeter spectrometer, but the data set was limited. The Soft X-ray Spectrometer (SXS) instrument of Hitomi was able to provide a more detailed picture of X-ray calorimeter background, with more than 360 ks of data while pointed at the Earth, and a comparable amount of blank-sky data. These data are important not only for analyzing SXS science data, but also for categorizing the contributions to the NXB in X-ray calorimeters as a class. In this paper, we present the contributions to the SXS NXB, the types and effectiveness of the screening, the interaction of the screening with the broad-band redistribution, and the residual background spectrum as a function of magnetic cut-off rigidity. The orbit-averaged SXS NXB in the range 0.3-12 keV was 4 × 10(exp −2) counts s(exp −1) -sq cm. This very low background in combination with groundbreaking spectral resolution gave SXS unprecedented sensitivity to weak spectral lines.

Kilbourne, Caroline A.↗
DOE OSTI2023

Recent progress on in-medium properties of heavy mesons from finite-temperature EFTs

Mesons with heavy flavor content are an exceptional probe of the hot QCD medium produced in heavy-ion collisions. In the past few years, significant progress has been made toward describing the modification of the properties of heavy mesons in the hadronic phase at finite temperature. Ground-state and excited-state thermal spectral properties can be computed within a self-consistent many-body approach that employs appropriate hadron-hadron effective interactions, providing a unique opportunity to confront hadronic Effective Field Theory predictions with recent and forthcoming lattice QCD simulations and experimental data. In this article, we revisit the application of the imaginary-time formalism to extend the calculation of unitarized scattering amplitudes from the vacuum to finite temperature. These methods allow us to obtain the ground-state thermal spectral functions. The thermal properties of the excited states that are dynamically generated within the molecular picture are also directly accessible. We present here the results of this approach for the open-charm and open-bottom sectors. We also analyze how the heavy-flavor transport properties, which are strongly correlated to experimental observables in heavy-ion collisions, are modified in hot matter. In particular, transport coefficients can be computed using an off-shell kinetic theory that is fully consistent with the effective theory describing the scattering processes. The results of this procedure for both charm and bottom transport coefficients are briefly discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1984

High Latitude Ionospheric Structure

The Earth's ionosphere is an important element in solar-terrestrial energy transfer processes. As a major terrestrial sink for many solar and magnetospheric events, the ionosphere has characteristic features that are traced to such seemingly remote phenomena as solar flares, radiation belt wave-particle interactions and magnetospheric substorms. In considering the multiple of solar-terrestrial plasma interactions, it is important to recognize that the high-latitude ionosphere is not altogether a simple receptor of various energy deposition processes. The high-altitude ionosphere plays an active feedback role by controlling the conductivity at the base of far-reaching magnetic field lines and by providing a plasma source for the magnetosphere. Indeed, the role of the ionosphere during magnetospheric substorms is emerging as a topic for meaningful study in the overall picture of magnetospheric-ionospheric coupling.

Source record↗
DOE OSTI2021

Oxidation of Cu 2 O(111) by NO 2 : An Ambient Pressure X-ray Photoelectron Spectroscopy Study

With NO x persisting as a problematic pollutant, understanding the interactions and reactivity of NO x species at atmospherically relevant pressures with surfaces remains essential. Synchrotron-based ambient pressure x-ray photoelectron spectroscopy (APXPS) and near-edge x-ray absorption spectroscopy fine structure (NEXAFS) were used to investigate the interactions of NO2 with a Cu 2 O(111) surface. The NEXAFS data reveals a pressure dependence of the oxidation of the Cu 2 O surface to CuO by NO 2 . APXPS results show NO 2 chemi- and physisorption on the Cu 2 O surface and decomposition to NO and O, or to N and O, with the amount of the species also being pressure dependent. Finally, the combination of the two spectroscopic techniques shows a comprehensive picture of NO 2 adsorption with implications for catalysis, gas sensing, and gas filtration materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRSDate not supplied

How Is the Solar Wind Shocked? A Distribution-Function Perspective From the MMS Mission

In this talk, we will discuss how plasma distribution functions from the Magnetospheric Multiscale (MMS) mission transformed the picture on how the solar wind is shocked. For quasi-parallel shocks with typical Alfven Mach numbers, we will examine how ion deceleration, reflection, and thermalization take place, and illustrate how the new picture expands on the framework envisioned by Schwartz and Burgess in 1991. For quasi-perpendicular shocks with the range of Alfven Mach numbers (~1-60) captured by MMS, we will examine examples showing the processes of ion and electron thermalization go beyond the existing paradigm and call for future investigation. The knowledge advanced by MMS measurements provides a ground to understand planetary shocks in our solar system as well as astrophysical shocks arising from stellar wind interaction with exoplanets and supernova remnants.

Li-Jen Chen↗
DOE OSTI2023

Enhancement of chiral edge currents in ($d$+1)-dimensional atomic Mott-band hybrid insulators

We consider the effect of a local interatomic repulsion on synthetic heterostructures where a discrete synthetic dimension is created by Raman processes on top of SU(N) S U ( N ) -symmetric two-dimensional lattice systems. At a filling of one fermion per site, increasing the interaction strength, the system is driven towards a Mott state which is adiabatically connected to a band insulator. The chiral currents associated with the synthetic magnetic field increase all the way to the Mott transition, where they reach the maximum value, and they remain finite in the whole insulating state. The transition towards the Mott-band insulator is associated with the opening of a gap within the low-energy quasiparticle peak, while a mean-field picture is recovered deep in the insulating state.

74 ATOMIC AND MOLECULAR PHYSICS↗
NASA NTRS1983

Multistation measurements of high-latitude ionospheric convection

Satellite and ground-based observations of the ionospheric drift velocity taken during a MITHRAS campaign have been combined to determine instantaneous pictures of the high-latitude convection pattern. These data, taken when the interplanetary magnetic field has a relatively stable southward/away orientation, show the existence of an asymmetric convection pattern under these conditions. A stability in the high latitude convection geometry can also be seen and changes in response to magnetic disturbances are inferred. Changes in the convection pattern as the interplanetary field turns northward possibly provide some information about the nature of the magnetosphere-solar wind interaction.

Heelis, R. A.↗
NASA NTRS1990

SMM mesospheric ozone measurements

The main objective was to understand the secular and seasonal behavior of ozone in the lower mesosphere, 50 to 70 km. This altitude region is important in understanding the factors which determine ozone behavior. A secondary objective is the study of stratospheric ozone in the polar regions. Use is made of results from the SBUV satellite borne instrument. In the Arctic the interaction between chlorine compounds and low molecular weight hydrocarbons is studied. More than 30,000 profiles were obtained using the UVSP instrument on the SMM spacecraft. Several orbits of ozone data per day were obtained allowing study of the current rise in solar activity from the minimum until the present. Analysis of Nimbus 7 SBUV data in Antarctic spring indicates that ozone is depleted within the polar vortex relative to ozone outside the vortex. This depletion confirms the picture of ozone loss at altitudes where polar stratospheric clouds exist. In addition, there is ozone loss above the cloud level indicating that there is another mechanism in addition to ozone loss initiated by heterogeneous chlorine reactions on cloud particles.

Aikin, A. C.↗
NASA NTRS2023

Information Systems Technology for NASA Earth Systems Digital Twins (ESDT)

The term “Digital Twin” was first used in 2002 for product lifecycle management. Since then, Digital Twin concepts have been proposed in various domains until very recently for Earth Science. For NASA’s Advanced Information Systems Technology (AIST) Program, an Earth System Digital Twin (ESDT) is defined as composed of three components: 1. A Digital Replica, i.e., an integrated picture of the past and current states of Earth systems 2. Forecasting capabilities, providing an integrated picture of how Earth systems will evolve in the future from the current state 3. Impact Assessment capabilities, providing an integrated picture of how Earth systems could evolve under different hypothetical what-if scenarios. Developing such a vision will require technologies related to: integrating continuous observations from various disparate sources; developing frameworks that builds on inter-connected models; improving the speed and accuracy of integrated prediction, analysis and visualization capabilities (e.g., by using machine learning); and utilizing causality and uncertainty quantification to improve our understanding of the evolution of Earth Science systems as a function of their interactions with other Earth and human systems. In addition, AIST is also investigating interoperability standards to federate multiple Digital Twins, as well as computational resources required by those systems.

Earth Science Remote Sensing; Information Systems↗
DOE OSTI2023

Impact of crowding on the diversity of expanding populations

Crowding effects critically impact the self-organization of densely packed cellular assemblies, such as biofilms, solid tumors, and developing tissues. When cells grow and divide, they push each other apart, remodeling the structure and extent of the population’s range. Recent work has shown that crowding has a strong impact on the strength of natural selection. However, the impact of crowding on neutral processes, which controls the fate of new variants as long as they are rare, remains unclear. Here, we quantify the genetic diversity of expanding microbial colonies and uncover signatures of crowding in the site frequency spectrum. By combining Luria–Delbrück fluctuation tests, lineage tracing in a novel microfluidic incubator, cell-based simulations, and theoretical modeling, we find that the majority of mutations arise behind the expanding frontier, giving rise to clones that are mechanically “pushed out” of the growing region by the proliferating cells in front. These excluded-volume interactions result in a clone-size distribution that solely depends on where the mutation first arose relative to the front and is characterized by a simple power law for low-frequency clones. Our model predicts that the distribution depends on a single parameter—the characteristic growth layer thickness—and hence allows estimation of the mutation rate in a variety of crowded cellular populations. Combined with previous studies on high-frequency mutations, our finding provides a unified picture of the genetic diversity in expanding populations over the whole frequency range and suggests a practical method to assess growth dynamics by sequencing populations across spatial scales.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1993

Fluctuations of total ozone and their relationship to stratospheric air motions

The origin of fluctuations of total ozone and the interactions that take place between the distribution of total ozone and the circulation of the troposphere are investigated on the basis of observations of total ozone from Nimbus 7 TOMS together with contemporaneous analyses of the circulation. It is shown that a sizable component of total ozone variability is explained by the quasi-columnar motion of air in the lower stratosphere. The development also suggests that in combination with isentropic analyses, total ozone measurements can provide a detailed picture of air motions in the lower stratosphere. Distributions of ozone column abundance and pressure on the 375-K isentropic surface for the Northern and Southern Hemispheres are illustrated.

Salby, Murry L.↗
DOE OSTI2022

“Self-trapping” in solar cell hybrid inorganic-organic perovskite absorbers

In the simplest picture, a “self-trapped” polaron forms when an excess electron or hole deforms a crystal lattice, creating a potential well with bound states. Properties of self-trapped polarons in methylammonium lead iodide perovskite (MAPbI 3 ), which is widely used as solar cell absorber, are of great interest, and are a subject of ongoing investigations and debates concerning the existence of large polarons with the co-presence of metastable self-trapping. Herein, we employ a self-interaction-free density functional theory method to investigate the stability of small polarons in tetragonal MAPbI 3 phase. The electron small polaron is found to be unstable, while the hole small polaron is found to be metastable at realistic operation temperatures of solar cells. Further, the hole polaron is found to have a hole band close to the conduction band, which in conjunction with its metastability suggests that small polarons will have an appreciable effect on charge-carrier recombinations in MAPbI 3 . Further, in this study, we posit that the existence of the metastable polarons in addition to the large polarons may explain the experimentally observed non-monotonic temperature dependence of bimolecular charge-carrier recombination rate in tetragonal MAPbI 3 phase.

14 SOLAR ENERGY↗
NASA NTRS1991

On the influence of the magnetization of a modal solar wind on a laboratory magnetosphere

The interaction of a magnetized plasma beam with a stationary dipole field, analogous to the interaction of the solar wind with the earth's magnetosphere, is explored in a laboratory experiment. Experimental parameters are chosen to scale qualitatively similar to the parameters in the earth's magnetosphere. It is found that the magnetization of the laboratory 'solar wind', generated by injecting a plasma across a preexisting magnetic field, requires a certain minimum magnetic field strength. Differences between the resulting magnetospheres for northward and southward 'solar wind' or 'interplanetary' magnetic fields (IMF) are demonstrated by global pictures and by magnetic field measurements above the north polar region. These measurements show patterns of the variation of the transverse field component which are similar to those found by satellite measurements above the earth. This indicates the presence of similar field-aligned current systems. Particularly, the presence (for northward IMF) and absence (for southward IMF) of the pattern attributed to the 'NBZ' (northward Bz) current system are demonstrated.

Rahman, H. U.↗
NASA NTRS1994

The development and validation of command schedules for SeaWiFS

An automated method for developing and assessing spacecraft and instrument command schedules is presented for the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) project. SeaWiFS is to be carried on the polar-orbiting SeaStar satellite in 1995. The primary goal of the SeaWiFS mission is to provide global ocean chlorophyll concentrations every four days by employing onboard recorders and a twice-a-day data downlink schedule. Global Area Coverage (GAC) data with about 4.5 km resolution will be used to produce the global coverage. Higher resolution (1.1 km resolution) Local Area Coverage (LAC) data will also be recorded to calibrate the sensor. In addition, LAC will be continuously transmitted from the satellite and received by High Resolution Picture Transmission (HRPT) stations. The methods used to generate commands for SeaWiFS employ numerous hierarchical checks as a means of maximizing coverage of the Earth's surface and fulfilling the LAC data requirements. The software code is modularized and written in Fortran with constructs to mirror the pre-defined mission rules. The overall method is specifically developed for low orbit Earth-observing satellites with finite onboard recording capabilities and regularly scheduled data downlinks. Two software packages using the Interactive Data Language (IDL) for graphically displaying and verifying the resultant command decisions are presented. Displays can be generated which show portions of the Earth viewed by the sensor and spacecraft sub-orbital locations during onboard calibration activities. An IDL-based interactive method of selecting and testing LAC targets and calibration activities for command generation is also discussed.

Woodward, Robert H.↗
NASA NTRS2005

System Developed for Bulk Flow Imaging of a Two-Phase Fluid in a Cylindrical Couette

The Microgravity Observation of Bubble Interactions (MOBI) experiment is working to better understand the physics of gas-liquid suspensions. To study such suspensions, researchers generate bubbles in a large cylindrical flow channel. Then, they use various types of instrumentation, including video imaging, to study the bubbly suspension. Scientists will need a camera view of the majority of the gas-liquid suspension inside of the couette in order to gather the information needed from the MOBI experiment. This will provide the scientists with a qualitative picture of the flow that may indicate flow instabilities or imperfect axial mixing inside the couette. These requirements pose a significant challenge because the imaging and lighting system must be confined to a very tight space since the space available on the International Space Station experiment racks is very limited. In addition, because of the large field of view needed and the detail needed to see the gas-liquid suspension behavior in the image, a digital video camera with high resolution (1024 by 1024 pixels) had to be used. Although the high-resolution camera will provide scientists with the image quality they need, it left little space on the experiment rack for the lighting system. Many configurations were considered for the lighting system, including front-lighting and back-lighting, but because of mechanical design limitations with the couette, back-lighting was not an option.

Juergens, Jeffrey R.↗
DOE OSTI2020

Electron-phonon drag enhancement of transport properties from a fully coupled ab initio Boltzmann formalism

We present a combined treatment of the nonequilibrium dynamics and transport of electrons and phonons by carrying out ab initio calculations of the fully coupled electron and phonon Boltzmann transport equations. We find that the presence of mutual drag between the two carriers causes the thermopower to be enhanced and dominated by the transport of phonons, rather than electrons as in the traditional semiconductor picture. Drag also strongly boosts the intrinsic electron mobility, thermal conductivity and the Lorenz number. Impurity scattering is seen to suppress the drag enhancement of the thermal and electrical conductivities, while having weak effects on the enhancement of the Lorenz number and thermopower. We demonstrate these effects in n-doped 3C-SiC at room temperature, and explain their origins. This work establishes the roles of microscopic scattering mechanisms in the emergence of strong drag effects in the transport of the interacting electron-phonon gas.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗