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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 937 records · Page 52
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

THE COMPLEX CIRCUMNUCLEAR ENVIRONMENT OF THE BROAD-LINE RADIO GALAXY 3C 390.3 REVEALED BY CHANDRA HETG

We present the first high spectral resolution X-ray observation of the broad-line radio galaxy 3C 390.3 obtained with the high-energy transmission grating spectrometer on board the Chandra X-ray Observatory . The spectrum shows complex emission and absorption features in both the soft X-rays and Fe K band. We detect emission and absorption lines in the energy range E = 700–1000 eV associated with ionized Fe L transitions (Fe XVII–XX). An emission line at the energy of E ≃ 6.4 keV consistent with the Fe K α is also observed. Our best-fit model requires at least three different components: (i) a hot emission component likely associated with the hot interstellar medium in this elliptical galaxy with temperature kT = 0.5 ± 0.1 keV; (ii) a warm absorber with ionization parameter log ξ = 2.3 ± 0.5 erg s{sup −1} cm, column density log N {sub H} = 20.7 ± 0.1 cm{sup −2}, and outflow velocity v {sub out} < 150 km s{sup −1}; and (iii) a lowly ionized reflection component in the Fe K band likely associated with the optical broad-line region or the outer accretion disk. These evidences suggest the possibility that we are looking directly down the ionization cone of this active galaxy and that the central X-ray source only photoionizes along the unobscured cone. This is overall consistent with the angle-dependent unified picture of active galactic nuclei.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2012

Error Reduction Methods for Integrated-path Differential-absorption Lidar Measurements

We report new modeling and error reduction methods for differential-absorption optical-depth (DAOD) measurements of atmospheric constituents using direct-detection integrated-path differential-absorption lidars. Errors from laser frequency noise are quantified in terms of the line center fluctuation and spectral line shape of the laser pulses, revealing relationships verified experimentally. A significant DAOD bias is removed by introducing a correction factor. Errors from surface height and reflectance variations can be reduced to tolerable levels by incorporating altimetry knowledge and "log after averaging", or by pointing the laser and receiver to a fixed surface spot during each wavelength cycle to shorten the time of "averaging before log".

averging before log↗
DOE OSTI2018

Utah FORGE: Observation Well Data

This archive contains temperature data for Roosevelt Hot Springs observation wells OH-1, OH-4, OH-5 and OH-7. There are also mud logs for OH-4. These are old datasets obtained from Rocky Mountain Power for use in the Utah FORGE project. Temperature data were collected in the 1970s and 1980s.

15 GEOTHERMAL ENERGY↗
DOE OSTI2015

Pore connectivity, electrical conductivity, and partial water saturation: Network simulations

Abstract The electrical conductivity of brine‐saturated rock is predominantly dependent on the geometry and topology of the pore space. When a resistive second phase (e.g., air in the vadose zone and oil/gas in hydrocarbon reservoirs) displaces the brine, the geometry and topology of the pore space occupied by the electrically conductive phase are changed. We investigated the effect of these changes on the electrical conductivity of rock partially saturated with brine. We simulated drainage and imbibition as invasion and bond percolation processes, respectively, in pipe networks assumed to be perfectly water‐wet. The simulations included the formation of a water film in the pipes invaded by the nonwetting fluid. During simulated drainage/imbibition, we measured the changes in resistivity index as well as a number of relevant microstructural parameters describing the portion of the pore space saturated with water. Except Euler topological number, all quantities considered here showed a significant level of “universality,” i.e., insensitivity to the type of lattice used (simple cubic, body‐centered cubic, or face‐centered cubic). Hence, the coordination number of the pore network appears to be a more effective measure of connectivity than Euler number. In general, the simulated resistivity index did not obey Archie's simple power law. In log‐log scale, the resistivity index curves displayed a substantial downward or upward curvature depending on the presence or absence of a water film. Our network simulations compared relatively well with experimental data sets, which were obtained using experimental conditions and procedures consistent with the simulations. Finally, we verified that the connectivity/heterogeneity model proposed by Bernabé et al. (2011) could be extended to the partial brine saturation case when water films were not present.

Li, M.↗
DOE OSTI2015

Theory and observations of upward field‐aligned currents at the magnetopause boundary layer

Abstract The dependence of the upward field‐aligned current density ( J || ) at the dayside magnetopause boundary layer is well described by a simple analytic model based on a velocity shear generator. A previous observational survey confirmed that the scaling properties predicted by the analytical model are applicable between 11 and 17 MLT. We utilize the analytic model to predict field‐aligned currents using solar wind and ionospheric parameters and compare with direct observations. The calculated and observed parallel currents are in excellent agreement, suggesting that the model may be useful to infer boundary layer structures. However, near noon, where velocity shear is small, the kinetic pressure gradients and thermal currents, which are not included in the model, could make a small but significant contribution to J || . Excluding data from noon, our least squares fit returns log( J ||,max_cal ) = (0.96 ± 0.04) log( J ||_obs ) + (0.03 ± 0.01) where J ||,max_cal = calculated J ||,max and J ||_obs = observed J || .

Wing, Simon↗
DOE OSTI2016

P and S wave responses of bacterial biopolymer formation in unconsolidated porous media

This study investigated the P and S wave responses and permeability reduction during bacterial biopolymer formation in unconsolidated porous media. Column experiments with fine sands, where the model bacteria Leuconostoc mesenteroides were stimulated to produce insoluble biopolymer, were conducted while monitoring changes in permeability and P and S wave responses. The bacterial biopolymer reduced the permeability by more than 1 order of magnitude, occupying ~10% pore volume after 38 days of growth. This substantial reduction was attributed to the bacterial biopolymer with complex internal structures accumulated at pore throats. S wave velocity (V S ) increased by more than ~50% during biopolymer accumulation; this indicated that the bacterial biopolymer caused a certain level of stiffening effect on shear modulus of the unconsolidated sediment matrix at low confining stress conditions. Whereas replacing pore water by insoluble biopolymer was observed to cause minimal changes in P wave velocity (VP) due to the low elastic moduli of insoluble biopolymer. The spectral ratio analyses revealed that the biopolymer formation caused a ~50-80% increase in P wave attenuation (1/Q P ) at the both ultrasonic and subultrasonic frequency ranges, at hundreds of kHz and tens of kHz, respectively, and a ~50-60% increase in S wave attenuation (1/Q S ) in the frequency band of several kHz. Our results reveal that in situ biopolymer formation and the resulting permeability reduction can be effectively monitored by using P and S wave attenuation in the ultrasonic and subultrasonic frequency ranges. Finally, this suggests that field monitoring using seismic logging techniques, including time-lapse dipole sonic logging, may be possible.

58 GEOSCIENCES↗
DOE OSTI2015

Prediction of MeV electron fluxes throughout the outer radiation belt using multivariate autoregressive models

The Van Allen radiation belts surrounding the Earth are filled with MeV-energy electrons. This region poses ionizing radiation risks for spacecraft that operate within it, including those in geostationary orbit (GEO) and medium Earth orbit. In order to provide alerts of electron flux enhancements, 16 prediction models of the electron log-flux variation throughout the equatorial outer radiation belt as a function of the McIlwain L parameter were developed using the multivariate autoregressive model and Kalman filter. Measurements of omnidirectional 2.3 MeV electron flux from the Van Allen Probes mission as well as >2 MeV electrons from the GOES 15 spacecraft were used as the predictors. Furthermore, we selected model explanatory parameters from solar wind parameters, the electron log-flux at GEO, and geomagnetic indices. For the innermost region of the outer radiation belt, the electron flux is best predicted by using the Dst index as the sole input parameter. For the central to outermost regions, at L≥4.8 and L ≥5.6, the electron flux is predicted most accurately by including also the solar wind velocity and then the dynamic pressure, respectively. The Dst index is the best overall single parameter for predicting at 3 ≤ L ≤ 6, while for the GEO flux prediction, the K P index is better than Dst. Finally, a test calculation demonstrates that the model successfully predicts the timing and location of the flux maximum as much as 2 days in advance and that the electron flux decreases faster with time at higher L values, both model features consistent with the actually observed behavior.

58 GEOSCIENCES↗
DOE OSTI2016

The connection between natural gas hydrate and bottom-simulating reflectors

Bottom-simulating reflectors (BSRs) on marine seismic data are commonly used to identify the presence of natural gas hydrate in marine sediments, although the exact relationship between gas hydrate and BSRs is undefined. In this paper, to clarify this relationship we compile a data set of probable gas hydrate occurrence as appraised from well logs of 788 industry wells in the northern Gulf of Mexico. We combine the well log data set with a data set of BSR distribution in the same area identified from 3-D seismic data. We find that a BSR increases the chances of finding gas hydrate by 2.6 times as opposed to drilling outside a BSR and that the wells within a BSR also contain thicker and higher resistivity hydrate accumulations. Finally, even so, over half of the wells drilled through BSRs have no detectable gas hydrate accumulations and gas hydrate occurrences and BSRs do not coincide in most cases.

58 GEOSCIENCES↗
DOE OSTI2017

The Impact of Frictional Healing on Stick-Slip Recurrence Interval and Stress Drop: Implications for Earthquake Scaling: The impact of healing on stick-slip

We report that interseismic frictional healing is an essential process in the seismic cycle. Observations of both natural and laboratory earthquakes demonstrate that the magnitude of stress drop scales with the logarithm of recurrence time, which is a cornerstone of the rate and state friction (RSF) laws. However, the origin of this log linear behavior and short time “cutoff” for small recurrence intervals remains poorly understood. Here we use RSF laws to demonstrate that the back-projected time of null-healing intrinsically scales with the initial frictional state θ i . We explore this behavior and its implications for (1) the short-term cutoff time of frictional healing and (2) the connection between healing rates derived from stick-slip sliding versus slide-hold-slide tests. We use a novel, continuous solution of RSF for a one-dimensional spring-slider system with inertia. The numerical solution continuously traces frictional state evolution (and healing) and shows that stick-slip cutoff time also scales with frictional state at the conclusion of the dynamic slip process θ i (=D c /V peak ). This numerical investigation on the origins of stick-slip response is verified by comparing laboratory data for a range of peak slip velocities. Slower slip motions yield lesser magnitude of friction drop at a given time due to higher frictional state at the end of each slip event. In conclusion, our results provide insight on the origin of log linear stick-slip evolution and suggest an approach to estimating the critical slip distance on faults that exhibit gradual accelerations, such as for slow earthquakes.

58 GEOSCIENCES↗
DOE OSTI2017

Analysis of albedo versus cloud fraction relationships in liquid water clouds using heuristic models and large eddy simulation: ALBEDO VERSUS CLOUD FRACTION RELATIONSHIPS

The relationship between the albedo of a cloudy scene $A$ and cloud fraction f c is studied with the aid of heuristic models of stratocumulus and cumulus clouds. Existing work has shown that scene albedo increases monotonically with increasing cloud fraction but that the relationship varies from linear to superlinear. The reasons for these differences in functional dependence are traced to the relationship between cloud deepening and cloud widening. When clouds deepen with no significant increase in f c (e.g., in solid stratocumulus), the relationship between$A$ and f c is linear.When clouds widen as they deepen, as in cumulus cloud fields, the relationship is superlinear. A simple heuristic model of a cumulus cloud field with a power law size distribution shows that the superlinear $A$-f c behavior is traced out either through random variation in cloud size distribution parameters or as the cloud field oscillates between a relative abundance of small clouds (steep slopes on a log-log plot) and a relative abundance of large clouds (flat slopes). Oscillations of this kind manifest in large eddy simulation of trade wind cumulus where the slope and intercept of the power law fit to the cloud size distribution are highly correlated. Further analysis of the large eddy model-generated cloud fields suggests that cumulus clouds grow larger and deeper as their underlying plumes aggregate; this is followed by breakup of large plumes and a tendency to smaller clouds. The cloud and thermal size distributions oscillate back and forth approximately in unison.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Inferring subsurface heterogeneity from push-drift tracer tests

In this study, we consider the late-time tailing in a tracer test performed with a push-drift methodology (i.e., quasi-radial injection followed by drift under natural gradient). Numerical simulations of such tests are performed on 1000 multi-Gaussian 2-D log-hydraulic conductivity field realizations of varying heterogeneity, each under eight distinct mean flow directions. The ensemble pdfs of solute return times are found to exhibit power law tails for each considered variance of the log-hydraulic conductivity field, σ$2\atop{ln K}$. The tail exponent is found to relate straightforwardly to σ$2\atop{ln K}$ and, within the parameter space we explored, to be independent of push-phase pumping rate, pumping duration, and local-scale dispersivity. We conjecture that individual push-drift tracer tests in wells with screened intervals much greater than the vertical correlation length of the aquifer will exhibit quasi-ergodicity and that their tail exponent may be used to infer σ$2\atop{ln K}$. Lastly, we calibrate a predictive relationship of this sort from our Monte Carlo study, and apply it to data from a push-drift test performed at a site of approximately known heterogeneity—closely matching the existing best estimate of heterogeneity.

58 GEOSCIENCES↗
DOE OSTI2019

Scaling-Up of Nano-Architected Microstructures: A Mechanical Assessment

Nano– and micro–architected materials generated by ultra–high–resolution 3D printing techniques, such as two–photon polymerization direct laser writing (TPP–DLW) or projection micro–stereolithography (PμSL), have garnered great interest due to their ability to achieve exceptional combinations of material properties. The scalability of these materials, however, remains a crucial challenge as larger high–resolution samples require stitching smaller blocks of the structure of interest together. Herein, scaling techniques and testing methodologies to investigate the effect of stitching on the integrity and mechanical behavior of TPP–DLW parts under tensile load are explored. Specifically, stitched log–pile I–beam specimens with relative densities of 21.5% and 54.7% are tested herein. The micro–tensile tests reveal that the higher–density log–pile samples exhibit brittle behavior with fracture loads at least four times higher than those of lower–density samples. The location of sample failure depends on the type of stitch introduced in the sample, as well as on the relative sample density. Altogether, this study highlights the importance of stitching techniques and relative density for the design of nano– and micro–architected materials.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Charge Transport in Highly Heterogeneous Natural Carbonaceous Materials

Abstract Natural carbonaceous materials (NCMs) have recently emerged as promising organic semiconducting materials for electronics and catalysis, although the fundamental picture of charge transport within NCM systems is still incomplete. Morphologically, NCMs exhibit reminiscence of disordered organic solids, yet the experimental measurements demonstrate a transport regime that surprisingly follows Mott's formula derived for variable‐range hopping in inorganic noncrystalline materials. With ab initio and kinetic Monte Carlo simulations, a temperature scaling is revealed between the Gaussian‐defect model log(σ) ∼ T −2 typical for organic matter and the Mott‐like log(σ) ∼ T −1/4 for a wide spectrum of intermolecular connectivity. As dominant transport descriptors, energy levels and coupling strengths are screened among 30 small molecules with varying sizes, shapes, sp 2 /sp 3 ratios, side chains, and functional groups. These analyses provide insight for the design of NCM electronics, and should also be applicable to disordered molecular materials in general.

Li, Huashan↗
DOE OSTI2023

Continuous precipitation‐filtration process for initial capture of a monoclonal antibody product using a four‐stage countercurrent hollow fiber membrane washing step

The significant increase in product titers, coupled with the growing focus on continuous bioprocessing, has renewed interest in using precipitation as a low‐cost alternative to Protein A chromatography for the primary capture of monoclonal antibody (mAb) products. In this work, a commercially relevant mAb was purified from clarified cell culture fluid using a tubular flow precipitation reactor with dewatering and washing provided by tangential flow microfiltration. The particle morphology was evaluated using an inline high‐resolution optical probe, providing quantitative data on the particle size distribution throughout the precipitation process. Data were obtained in both a lab‐built 2‐stage countercurrent washing system and a commercial countercurrent contacting skid that provided 4 stages of continuous washing. The processes were operated continuously for 2 h with overall mAb yield of 92 ± 3% and DNA removal of nearly 3 logs in the 4‐stage system. The high DNA clearance was achieved by selective redissolution of the mAb using a low pH acetate buffer. Host cell protein clearance was 0.59 ± 0.08 logs, comparable to that based on model predictions. The process mass intensity was slightly better than typical Protein A processes and could be significantly improved by preconcentration of the antibody feed material.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Photoinactivation of Planktonic and Biofilm Forms of Escherichia coli through the Action of Cationic Zinc(II) Phthalocyanines

Abstract Novel water‐soluble zinc(II) phthalocyanines (ZnPc) peripherally substituted with 4‐dimethylaminopyridine (DMAP) units (ZnPc 1 – 2 ) and the corresponding quaternized derivatives (ZnPc 1 a – 2 a ) were synthesized and their photodynamic inactivation (PDI) efficiency against a Gram‐negative bacterium, a recombinant bioluminescent Escherichia coli strain either in planktonic or biofilm form, was investigated. The analysis of the photophysical properties revealed that the increase in the number of DMAP units on ZnPc shifted the absorption and emission band in aqueous media to the red region. The presence of multi‐positive charges on ZnPc derivatives prevented aggregation and enhances the solubility in aqueous media. The quaternized derivatives ZnPc 1 a and 2 a displayed good stability and promising efficacy to generate singlet oxygen ( 1 O 2 ). The affinity of the amphiphilic ZnPc 1 – 2 and quaternized ZnPc 1 a – 2 a to planktonic bacterial cells corresponded to an average uptake of ∼10 6 PS molecules.CFU −1 . The PDI assays conducted with planktonic cells and biofilms of E. coli show that irradiation with red or white light (150 mW.cm −2 ) in the presence of 20 μM of ZnPc derivatives caused an effective inactivation. ZnPc 1 a and ZnPc 2 a exhibited the highest inactivation efficiency, particularly of the planktonic form, causing a 5 log‐scale (99.99 %) reduction in bioluminescence. The inactivation factor for biofilms was 99 % (2 log). ZnPc 1 a and ZnPc 2 a can be regarded as promising photosensitizers for the photodynamic inactivation of Gram‐negative bacteria.

Lourenço, Leandro M. O.↗
DOE OSTI2019

A preliminary study of the gas hydrate stability zone in a gas hydrate potential region of China

Abstract Due to its significance for gas hydrate accumulation, the gas hydrate stability zone (GHSZ) is an essential condition for successful gas hydrate exploration and is usually controlled by three main factors: gas components, geothermal gradient, and permafrost thickness. Based on the core and conventional log data of gas hydrate potential region, the CSMHYD program was adopted to simulate the influences of above three factors on the thickness of the GHSZ. When the gas components of the gas hydrate were CH 4 , C 2 H 6 , and C 3 H 8 , with the CH 4 percentage ranging from 50% to 100%, the average GHSZ thickness can reach 1000 m according to the forward simulation results. When the gas hydrate was composed of CH 4 and one of C 2 H 6 , C 3 H 8 , H 2 S, and CO 2 , the influence order of the above four gases on the thickness of GHSZ is as follows: H 2 S ＞ C 2 H 6 ＞ C 3 H 8 ＞ CO 2 . Under the gas components of 90% CH 4 , 5% C 2 H 6, and 5% C 3 H 8 , the thickness of GHSZ decreased rapidly as the geothermal gradient increased following an exponential relation with a correlation of 99.92% and increased slowly as permafrost thickness increased following a linear relation with a correlation of 99.9%. In addition, the thickness of a gas hydrate favorable reservoir was determined by comprehensive log methods as 500 m. We conclude that a reservoir within 500 m below the permafrost layer is favorable for gas hydrate reservoir formation.

Xiao, Kun↗
DOE OSTI2023

A phased workflow to define permit‐ready locations for large volume CO 2 injection and storage

Abstract To‐date, only two UIC Class VI permits have been issued by the US Environmental Protection Agency. We illustrate a four‐phase workflow to first identify regional storage resources and then down‐select sites to yield permit‐ready locations that can accept and store large volumes of CO 2 . Specific permit requirements should guide objectives and define deliverables of respective workflow phases. In the first phase we used available regional data and screened structure and injection zones to locate resources that match CO 2 volumes planned to be captured. Available data were also used to assess presence and depth of usable groundwater, the key resource being protected via permitting. We then used advanced, closed‐form, analytical solutions (EASiTool) to estimate CO 2 injectivity into each hydrologically connected injection compartment. In the second phase we acquired and conditioned additional wireline logs and leased available seismic datasets. We interpreted the depositional systems from wireline well‐log character and mapped sandbody geometry to interpolate injection and confining‐zone distribution. Using available data, we mapped faults and locations of freshwater and overpressure (or other capacity‐limiting geologic parameters) in more detail. In the third phase, we used the augmented geologic data to develop a static model for the selected area, extracted the areas of highest interest, and generated and ran dynamic (flow) models. In a fourth phase, we reduced major uncertainties identified in earlier phases. Our case study indicates that to complete preparation of a permit application requires (1) improved lithologic characterization information (thicknesses and horizontal and vertical connectivity) and (2) better definition of poorly defined local faults. © 2023 The Authors. Greenhouse Gases: Science and Technology published by Society of Chemical Industry and John Wiley & Sons Ltd.

58 GEOSCIENCES↗