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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 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Predicting and Managing Lighting and Visibility for Human Operations in Space

Lighting is critical to human visual performance. On earth this problem is well understood and solutions are well defined and executed. Because the sun rises and sets on average every 45 minutes during Earth orbit, humans working in space must cope with ~ extremely dynamic lighting conditions varying from very low light conditions to severe glare and contrast conditions. For critical operations, it is essential that lighting conditions be predictable and manageable. Mission planners need to detelmine whether low-light video cameras are required or whether additional luminaires, or lamps, need to be flown . Crew and flight directors need to have up to date daylight orbit time lines showing the best and worst viewing conditions for sunlight and shadowing. Where applicable and possible, lighting conditions need to be part of crew training. In addition, it is desirable to optimize the quantity and quality of light because of the potential impacts on crew safety, delivery costs, electrical power and equipment maintainability for both exterior and interior conditions. Addressing these issues, an illumination modeling system has been developed in the Space Human Factors Laboratory at ASA Johnson Space Center. The system is the integration of a physically based ray-tracing package ("Radiance"), developed at the Lawrence Berkeley Laboratories, a human factors oriented geometric modeling system developed by NASA and an extensive database of humans and their work environments. Measured and published data has been collected for exterior and interior surface reflectivity; luminaire beam spread distribution, color and intensity and video camera light sensitivity and has been associated with their corresponding geometric models. Selecting an eye-point and one or more light sources, including sun and earthshine, a ~ snapshot of the light energy reaching the surfaces or reaching the eye point is computed. This energy map is then used to extract the required information needed for useful predictions. Using a validated, comprehensive illumination model integrated with empirically derived data, predictions of lighting and viewing conditions have been successfully used for Shuttle and Space Station planning and assembly operations. It has successfully balanced the needs for adequate human performance with the utili zation of resources. Keywords: Modeling, ray tracing, luminaires, refl ectivity, luminance, illuminance.

Maida, James C.↗
NASA NTRS2019

Atmospheric Correction for Coastal Waters Based on Multi-Angle Polarimetric Observations

Atmospheric correction is an essential procedure of ocean color remote sensing, which obtains water-leaving signals from satellite or airborne sensors. Due to the small percentage of the water leaving signals in the total measurement, atmospheric correction requires precise evaluation of the radiometric contributions from the aerosol and ocean surface. It is often challenging over coastal waters when absorbing aerosols are present and when water leaving signals in the near infrared spectral region are non-negligible. In this work, we report on a joint retrieval algorithm that determines aerosol and ocean optical properties using the polarimetric measurements based on a coupled atmosphere and ocean radiative transfer model. Two bio-optical models are designed for ocean water properties. One model parameterizes the open ocean optical properties in terms of the concentration of chlorophyll a. The other is a generalized bio-optical model for coastal waters that describes the absorption and scattering by phytoplankton, colored dissolved organic matter and non-algal particles using multiple parameters. We applied the algorithm to the airborne Research Scanning Polarimeter (RSP) measurements acquired over both open and coastal ocean waters. Through the comparisons with in situ ocean color measurements, the flexibility and accuracy of the retrieval algorithm in retrieving aerosol and water leaving radiance properties are demonstrated under various aerosol and ocean water conditions.

Gao, Meng↗
NASA NTRS2010

Layered Model for Radiation-Induced Chemical Evolution of Icy Surface Composition on Kuiper Belt and Oort Cloud Bodies

The diversity of albedos and surface colors on observed Kuiper Belt and Inner Oort Cloud objects remains to be explained in terms of competition between primordial intrinsic versus exogenic drivers of surface and near-surface evolution. Earlier models have attempted without success to attribute this diversity to the relations between surface radiolysis from cosmic ray irradiation and gardening by meteoritic impacts. A more flexible approach considers the different depth-dependent radiation profiles produced by low-energy plasma, suprathermal, and maximally penetrating charged particles of the heliospheric and local interstellar radiation environments. Generally red objects of the dynamically cold (low inclination, circular orbit) Classical Kuiper Belt might be accounted for from erosive effects of plasma ions and reddening effects of high energy cosmic ray ions, while suprathermal keV-MeV ions could alternatively produce more color neutral surfaces. The deepest layer of more pristine ice can be brought to the surface from meter to kilometer depths by larger impact events and potentially by cryovolcanic activity. The bright surfaces of some larger objects, e.g. Eris, suggest ongoing resurfacing activity. Interactions of surface irradiation, resultant chemical oxidation, and near-surface cryogenic fluid reservoirs have been proposed to account for Enceladus cryovolcanism and may have further applications to other icy irradiated bodies. The diversity of causative processes must be understood to account for observationally apparent diversities of the object surfaces.

Cooper, John F.↗
DOE OSTI2023

Predicting wind-driven spatial deposition through simulated color images using deep autoencoders

Abstract For centuries, scientists have observed nature to understand the laws that govern the physical world. The traditional process of turning observations into physical understanding is slow. Imperfect models are constructed and tested to explain relationships in data. Powerful new algorithms can enable computers to learn physics by observing images and videos. Inspired by this idea, instead of training machine learning models using physical quantities, we used images, that is, pixel information. For this work, and as a proof of concept, the physics of interest are wind-driven spatial patterns. These phenomena include features in Aeolian dunes and volcanic ash deposition, wildfire smoke, and air pollution plumes. We use computer model simulations of spatial deposition patterns to approximate images from a hypothetical imaging device whose outputs are red, green, and blue (RGB) color images with channel values ranging from 0 to 255. In this paper, we explore deep convolutional neural network-based autoencoders to exploit relationships in wind-driven spatial patterns, which commonly occur in geosciences, and reduce their dimensionality. Reducing the data dimension size with an encoder enables training deep, fully connected neural network models linking geographic and meteorological scalar input quantities to the encoded space. Once this is achieved, full spatial patterns are reconstructed using the decoder. We demonstrate this approach on images of spatial deposition from a pollution source, where the encoder compresses the dimensionality to 0.02% of the original size, and the full predictive model performance on test data achieves a normalized root mean squared error of 8%, a figure of merit in space of 94% and a precision-recall area under the curve of 0.93.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS2015

Learning LM Specificity for Ganglion Cells

Unsupervised learning models have been proposed based on experience (Ahumada and Mulligan, 1990;Wachtler, Doi, Lee and Sejnowski, 2007) that allow the cortex to develop units with LM specific color opponent receptive fields like the blob cells reported by Hubel and Wiesel on the basis of visual experience. These models used ganglion cells with LM indiscriminate wiring as inputs to the learning mechanism, which was presumed to occur at the cortical level.

retinal ganglion cells↗
DOE OSTI2015

Stellar masses and star formation rates for 1 M galaxies from SDSS+WISE

We combine Sloan Digitital Sky Survey (SDSS) and WISE photometry for the full SDSS spectroscopic galaxy sample, creating spectral energy distributions (SEDs) that cover λ = 0.4–22 μm for an unprecedentedly large and comprehensive sample of 858,365 present-epoch galaxies. Using MAGPHYS, we then simultaneously and consistently model both the attenuated stellar SED and the dust emission at 12 and 22 μm, producing robust new calibrations for monochromatic mid-IR star formation rate (SFR) proxies. These modeling results provide the first mid-IR-based view of the bimodality in star formation activity among galaxies, exhibiting the sequence of star-forming galaxies (“main sequence”) with a slope of d log SFR/dlogM{sub ∗} = 0.80 and a scatter of 0.39 dex. We find that these new SFRs along the SF main sequence are systematically lower by a factor of 1.4 than those derived from optical spectroscopy. We show that for most present-day galaxies, the 0.4–22 μm SED fits can exquisitely predict the fluxes measured by Herschel at much longer wavelengths. Our analysis also illustrates that the majority of stars in the present-day universe are formed in luminous galaxies (∼L{sup ∗}) in and around the “green valley” of the color–luminosity plane. We make publicly available the matched photometry catalog and SED modeling results.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2001

Restraint of Liquid Jets by Surface Tension in Microgravity Modeled

Tension in Microgravity Modeled Microgravity poses many challenges to the designer of spacecraft tanks. Chief among these are the lack of phase separation and the need to supply vapor-free liquid or liquidfree vapor to the spacecraft processes that require fluid. One of the principal problems of phase separation is the creation of liquid jets. A jet can be created by liquid filling, settling of the fluid to one end of the tank, or even closing a valve to stop the liquid flow. Anyone who has seen a fountain knows that jets occur in normal gravity also. However, in normal gravity, the gravity controls and restricts the jet flow. In microgravity, with gravity largely absent, jets must be contained by surface tension forces. Recent NASA experiments in microgravity (Tank Pressure Control Experiment, TPCE, and Vented Tank Pressure Experiment, VTRE) resulted in a wealth of data about jet behavior in microgravity. VTRE was surprising in that, although it contained a complex geometry of baffles and vanes, the limit on liquid inflow was the emergence of a liquid jet from the top of the vane structure. Clearly understanding the restraint of liquid jets by surface tension is key to managing fluids in low gravity. To model this phenomenon, we need a numerical method that can track the fluid motion and the surface tension forces. The fluid motion is modeled with the Navier-Stokes equation formulated for low-speed incompressible flows. The quantities of velocity and pressure are placed on a staggered grid, with velocity being tracked at cell faces and pressure at cell centers. The free surface is tracked via the introduction of a color function that tracks liquid as 1/2 and gas as -1/2. A phase model developed by Jacqmin is used. This model converts the discrete surface tension force into a barrier function that peaks at the free surface and decays rapidly. Previous attempts at this formulation have been criticized for smearing the interface. However, by sharpening the phase function, double gridding the fluid function, and using a higher order solution for the fluid function, interface smearing is avoided. These equations can be rewritten as two coupled Poisson equations that also include the velocity. The method of solution is as follows: first, the phase equations are solved from this solution, a velocity field is generated, then a successive overrelaxation scheme is used to solve for a pressure field consistent with the velocity solution. After the code was implemented in axisymmetric form and verified by several test cases, the drop tower runs of Aydelott were modeled. The model handed the free-surface deformation quite nicely, even to the point of modeling geyser growth in the regime where the free surface was no longer restrained. A representative run is shown.

Chato, David J.↗
DOE OSTI2015

Resolve survey photometry and volume-limited calibration of the photometric gas fractions technique

We present custom-processed ultraviolet, optical, and near-infrared photometry for the REsolved Spectroscopy of a Local VolumE (RESOLVE) survey, a volume-limited census of stellar, gas, and dynamical mass within two subvolumes of the nearby universe (RESOLVE-A and RESOLVE-B). RESOLVE is complete down to baryonic mass ∼10{sup 9.1−9.3} M{sub ⊙}, probing the upper end of the dwarf galaxy regime. In contrast to standard pipeline photometry (e.g., SDSS), our photometry uses optimal background subtraction, avoids suppressing color gradients, and employs multiple flux extrapolation routines to estimate systematic errors. With these improvements, we measure brighter magnitudes, larger radii, bluer colors, and a real increase in scatter around the red sequence. Combining stellar mass estimates based on our optimized photometry with the nearly complete H i mass census for RESOLVE-A, we create new z = 0 volume-limited calibrations of the photometric gas fractions (PGF) technique, which predicts gas-to-stellar mass ratios (G/S) from galaxy colors and optional additional parameters. We analyze G/S-color residuals versus potential third parameters, finding that axial ratio is the best independent and physically meaningful third parameter. We define a “modified color” from planar fits to G/S as a function of both color and axial ratio. In the complete galaxy population, upper limits on G/S bias linear and planar fits. We therefore model the entire PGF probability density field, enabling iterative statistical modeling of upper limits and prediction of full G/S probability distributions for individual galaxies. These distributions have two-component structure in the red color regime. Finally, we use the RESOLVE-B 21 cm census to test several PGF calibrations, finding that most systematically under- or overestimate gas masses, but the full probability density method performs well.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2018

Quantifying Boreal Forest Structure and Composition Using UAV Structure from Motion

The vast extent and inaccessibility of boreal forest ecosystems are barriers to routine monitoring of forest structure and composition. In this research, we bridge the scale gap between intensive but sparse plot measurements and extensive remote sensing studies by collecting forest inventory variables at the plot scale using an unmanned aerial vehicle (UAV) and a structure from motion (SfM) approach. At 20 Forest Inventory and Analysis (FIA) subplots in interior Alaska, we acquired overlapping imagery and generated dense, 3D, RGB (red, green, blue) point clouds. We used these data to model forest type at the individual crown scale as well as subplot-scale tree density (TD), basal area (BA), and aboveground biomass (AGB). We achieved 85% cross-validation accuracy for five species at the crown level. Classification accuracy was maximized using three variables representing crown height, form, and color. Consistent with previous UAV-based studies, SfM point cloud data generated robust models of TD (r(sup 2) = 0.91), BA (r(sup 2) = 0.79), and AGB (r(sup 2) = 0.92), using a mix of plot- and crown-scale information. Precise estimation of TD required either segment counts or species information to differentiate black spruce from mixed white spruce plots. The accuracy of species-specific estimates of TD, BA, and AGB at the plot scale was somewhat variable, ranging from accurate estimates of black spruce TD (+/−1%) and aspen BA (−2%) to misallocation of aspen AGB (+118%) and white spruce AGB (−50%). These results convey the potential utility of SfM data for forest type discrimination in FIA plots and the remaining challenges to develop classification approaches for species-specific estimates at the plot scale that are more robust to segmentation error.

aboveground biomass↗
DOE OSTI2023

Axion-gauge coupling quantization with a twist

The possible couplings of an axion to gauge fields depend on the global structure of the gauge group. If the Standard Model gauge group is minimal, or equivalently if fractionally charged color-singlet particles are forbidden, then the QCD axion’s Chern-Simons couplings to photons and gluons obey correlated quantization conditions. Specifically, the photon coupling can have a fractional part which is a multiple of 1/3, but which is determined by the gluon coupling. A consequence of this result is that, among all theories with a minimal gauge group and minimal axion coupling to gluons, the smallest possible axion-photon amplitude |g aγγ | arises for E/N = 8/3. This provides a new motivation for experiments targeting this axion-photon coupling.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Exclusive J / ψ , ψ ( 2 s ) , and e + e - pair production in Au + Au ultraperipheral collisions at the BNL Relativistic Heavy Ion Collider

Measurements of exclusive J/ψ, ψ(2⁢s), and electron-positron (e + ⁢e - ) pair photoproduction in Au+Au ultraperipheral collisions are reported by the STAR experiment at $\sqrt{s_{NN}}$ = 200GeV. Here, we report several first measurements at the BNL Relativistic Heavy Ion Collider, which are (i) J/ψ photoproduction with large momentum transfer up to 2.2⁢(GeV/c) 2 , (ii) coherent J/ψ photoproduction associated with neutron emissions from nuclear breakup, (iii) the rapidity dependence of incoherent J/ψ photoproduction, (iv) the ψ⁡(2⁢s) photoproduction cross section at midrapidity, and (v) e + ⁢e - pair photoproduction up to high invariant mass of 6GeV/c 2 . For measurement (ii), the coherent J/ψ total cross section of γ + Au → J/ψ + Au as a function of the center-of-mass energy W γN has been obtained without photon energy ambiguities. The data are quantitatively compared with the Monte Carlo models STARlight, Sartre, BeAGLE, and theoretical calculations of gluon saturation with color glass condensate, nuclear shadowing with leading twist approximation, quantum electrodynamics, and the next-to-leading-order perturbative QCD. At the photon-nucleon center-of-mass energy of 25.0 GeV, the coherent and incoherent J/ψ cross sections of Au nuclei are found to be 71% ± 10% and 36% ± 7%, respectively, of that of free protons. These data provide an important experimental constraint for nuclear parton distribution functions and a unique opportunity to advance the understanding of the nuclear modification effect at the top RHIC energy.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Basis light front quantization for the charged light mesons with color singlet Nambu–Jona-Lasinio interactions

We apply the basis light front quantization (BLFQ) approach to describe the valence structures of the charged light meson ground states. Specifically, the light front wave functions of π ± , ρ ± , K ± and K∗ ± are obtained as the eigenvectors of the light front effective Hamiltonians with confinement potentials supplemented by the color singlet Nambu–Jona-Lasinio (NJL) interactions. We adjust our model such that the spectrum of these ground states and the charge radii of the pseudoscalar states agree with experimental results. We present the elastic form factors and parton distribution amplitudes (PDAs) as illustrations of the internal structures of the pseudoscalar pions and kaons in terms of valence quarks.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Bridging hadronic and vacuum structure by heavy quarkonia

We discuss the central and, mostly, spin-dependent potentials in heavy quarkonia $\overline{b}$$b$,$\overline{c}$$c$, with two goals in mind. The first is phenomenological: using the splitting between the 1S and 2S pairs, as well as the 1P and 2P quartet masses, we obtain pertinent matrix elements of all these potentials. The second is theoretical: using standard wave functions, we compute these matrix elements, quantifying the perturbative, nonperturbative and “string” contributions. The model for nonperturbative effects is a “dense instanton liquid model,” in which the QCD vacuum is made mostly of (strongly color correlated) instanton-anti-instanton pairs or “molecules.” Their contributions are calculated via standard Wilson lines, with or without extra powers of gauge fields. We find a reasonable description of all central, spin-spin, and spin-orbit forces at distances 𝑟 = 0–0.7 fm, relevant for $\overline{b}$$b$ and $\overline{c}$$c$ quarkonia.

Bound states↗
DOE OSTI2015

GUT-inspired supersymmetric model for h → γ γ and the muon g - 2

We study a grand unified theories inspired supersymmetric model with nonuniversal gaugino masses that can explain the observed muon g-2 anomaly while simultaneously accommodating an enhancement or suppression in the h→γγ decay channel. In order to accommodate these observations and m h ≅125 to 126 GeV, the model requires a spectrum consisting of relatively light sleptons whereas the colored sparticles are heavy. The predicted stau mass range corresponding to R γγ ≥1.1 is 100 GeV≲m τ˜ ≲200 GeV. The constraint on the slepton masses, particularly on the smuons, arising from considerations of muon g-2 is somewhat milder. The slepton masses in this case are predicted to lie in the few hundred GeV range. The colored sparticles turn out to be considerably heavier with m g˜ ≳4.5 TeV and m t˜₁ ≳3.5 TeV, which makes it challenging for these to be observed at the 14 TeV LHC.

Ajaib, M. Adeel↗
DOE OSTI2017

Baryogenesis from oscillations of charmed or beautiful baryons

Here, we propose a model for CP violating oscillations of neutral, heavy-flavored baryons into antibaryons at rates which are within a few orders of magnitude of their lifetimes. The flavor structure of the baryon violation suppresses neutron oscillations and baryon number violating nuclear decays to experimentally allowed rates. We also propose a scenario for producing such baryons in the early Universe via the out-of-equilibrium decays of a neutral particle, after hadronization but before nucleosynthesis. We find parameters where CP violating baryon oscillations at a temperature of a few MeV could result in the observed asymmetry between baryons and antibaryons. Additionally, part of the relevant parameter space for baryogenesis is potentially testable at Belle II via decays of heavy flavor baryons into an exotic neutral fermion. The model introduces four new particles: three light Majorana fermions and a colored scalar. The lightest of these fermions is typically long lived on collider timescales and may be produced in decays of bottom and possibly charmed hadrons.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Differences in halo-scale environments between type 1 and type 2 AGNs at low redshift

Using low-redshift (z<0.09) samples of active galactic nuclei (AGNs), normal galaxies and groups of galaxies selected from the Sloan Digital Sky Survey, we study the environments of Type 1 and Type 2 AGNs, both on small and large scales. Comparisons are made for galaxy samples matched in redshift, r-band luminosity, [O iii] luminosity, and also the position in groups (central or satellite). We find that Type 2 AGNs and normal galaxies reside in similar environments. Type 1 and Type 2 AGNs have similar clustering properties on large scales (≳1 h{sup −1} Mpc), but at scales smaller than 100 h{sup −1} kpc, Type 2s have significantly more neighbors than Type 1s (3.09 ± 0.69 times more for central AGNs at ≲30 h{sup −1} kpc). These results suggest that Type 1 and Type 2 AGNs are hosted by halos of similar masses, as can also be seen directly from the mass distributions of their host groups (∼10{sup 12} h{sup −1} M{sub ⊙} for centrals and ∼10{sup 13} h{sup −1} M{sub ⊙} for satellites). Type 2s have significantly more satellites around them, and the distribution of their satellites is also more centrally concentrated. The host galaxies of both types of AGNs have similar optical properties, but their infrared colors are significantly different. Our results suggest that the simple unified model based solely on torus orientation is not sufficient, but that galaxy interactions in dark matter halos must have played an important role in the formation of the dust structure, which obscures AGNs.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

A New Method for Aerosol Measurement Using Wide-field Photometry

We present a new method to measure the vertical aerosol optical depth (VAOD) during clear nights using a wide-field imager—a CCD camera with a photographic lens on an equatorial mount. A series of 30 s exposures taken at different altitudes above the horizon can be used to measure the VAOD with a precision better than 0.008 optical depths within a few minutes. Such a measurement does not produce any light and is thus suitable for use at sites where other astronomical instruments are located. The precision of the VAOD measurement depends on the laboratory calibration of spectral properties of the system and of the response of the camera electronics to varying illumination levels, as well as careful considerations of the details of stellar photometry and modeling of the dependence of the measured stellar flux, the star color, and the position within the field of view. The results obtained with robotic setups at the future sites of the Cerenkov Telescope Array show good internal consistency and agreement with simultaneous measurements from a Sun/Moon photometer located at the same sites.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1972

Photometry of late type stars

Broad band filter photometry for 57 bright stars of spectral type A2 discussed with peak instrument responses at 3320, 2980, 2460 and 1910 A. The data include nearly all usable filter observations of G, K and M types. Sampling is nearly complete for A and F giants and supergiants, with the exception of Cepheid variables. The basic results presented are relative digital counting rates obtained with a field-stop aperture of 10 minutes of arc. Characteristics of the four filter-photometer combinations and errors are discussed. Some observations require substantial correction if they are to represent the visually brightest star in the field. These corrections and the effects of interstellar reddening are discussed. The adjusted counts are then used to construct color-color diagrams and are compared to the recent SAO grid of model atmospheres.

Doherty, L. R.↗