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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 1,549 records · Page 86
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Assessment of Precipitating Marine Stratocumulus Clouds in the E3SMv1 Atmosphere Model: A Case Study from the ARM MAGIC Field Campaign

This paper presents a process-oriented evaluation of precipitating stratocumulus and its transition to cumulus in version 1 of the Energy Exascale Earth System Model (E3SMv1) using comprehensive case-study observations from a field campaign of the Atmospheric Radiation Measurement program (ARM). The E3SMv1 single-column model (SCM) of the marine boundary layer and its low clouds and precipitation are compared to observations including subcloud drizzle retrievals from a combination of Doppler radar and lidar backscatter measurements. Additionally, the SCM is also compared to a large-eddy simulation (LES) of the same case. The combination of advanced remote sensing observations and LES is a powerful framework to evaluate the physical parameterizations of large-scale models. Given the observed large-scale environment, the E3SMv1 SCM realistically represents the evolution of clouds and boundary layer structure during the stratocumulus-to-cumulus transition. The model well simulates the liquid water path and its diurnal cycle in the stratocumulus period as well as the two-layer vertical thermodynamic structure and lower cloud fraction in the transition period. E3SMv1’s success in simulating the cloud in the stratocumulus period permitted examination of its precipitation processes. Here problems were identified with E3SMv1 producing an unrealistically small subcloud precipitation fraction, an unrealistic double peak in the vertical profiles of precipitation mass, and drizzle that evaporates too close to the surface. Further model diagnostics determined that these unrealistic characteristics resulted from an overly long microphysics time step and an unrealistic parameterization of the precipitation fraction. These results imply that careful consideration of these issues is needed in order to better simulate precipitation processes in marine stratocumulus.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1994

A trajectory modeling investigation of the biomass burning-tropical ozone relationship

The hypothesis that tropical total O3 maxima seen by the TOMS satellite derive from African biomass burning has been tested using isentropic trajectory analyses with global meteorological data fields. Two case studies from the 1989 biomass burning season demonstrate that a large fraction of the air arriving at the location of TOMS O3 maxima passed over regions of intense burning. Other trajectories initiated at a series of points over Africa and the Atlantic suggest flight strategies for field studies to be conducted in September 1992.

Pickering, Kenneth E.↗
NASA NTRS2010

Interplanetary Magnetic Field Power Spectrum Variations: A VHO Enabled Study

The newly reprocessed high time resolution (11/22 vectors/sec) Wind mission interplanetary magnetic field data and the solar wind key parameter search capability of the Virtual Heliospheric Observatory (VHO) affords an opportunity to study magnetic field power spectral density variations as a function of solar wind conditions. In the reprocessed Wind Magnetic Field Investigation (MFI) data, the spin tone and its harmonics are greatly reduced that allows the meaningful fitting of power spectra to the approx.2 Hz limit above which digitization noise becomes apparent. The power spectral density is computed and the spectral index is fitted for the MHD and ion inertial regime separately along with the break point between the two for various solar wind conditions . The time periods of fixed solar wind conditions are obtained from VHO searches that greatly simplify the process. The functional dependence of the ion inertial spectral index and break point on solar wind plasma and magnetic field conditions will be discussed

Szabo, A.↗
NASA NTRS2011

Interplanetary Magnetic Field Power Spectrum Variations: A VHO Enabled Study

The newly reprocessed high time resolution (11/22 vectors/sec) Wind mission interplanetary magnetic field data and the solar wind key parameter search capability of the Virtual Heliospheric Observatory (VHO) affords an opportunity to study magnetic field power spectral density variations as a function of solar wind conditions. In the reprocessed Wind Magnetic Field Investigation (MFI) data, the spin tone and its harmonics are greatly reduced that allows the meaningful fitting of power spectra to the ~2 Hz limit above which digitization noise becomes apparent. The power spectral density is computed and the spectral index is fitted for the MHD and ion inertial regime separately along with the break point between the two for various solar wind conditions. The time periods of fixed solar wind conditions are obtained from VHO searches that greatly simplify the process. The functional dependence of the ion inertial spectral index and break point on solar wind plasma and magnetic field conditions will be discussed

Szabo, A.↗
DOE OSTI2020

Theoretical study of various nonlinear phenomena in plasma systems and scaling of magneto-inertial-fusion targets

Plasma physics is an exciting field of study with a wide variety of nonlinear processes that come into play. Examples of such processes include the interaction of small-scale turbulence with large-scale plasma structures and the nonlinear saturation of plasma instabilities, for example those of magneto-hydrodynamical nature. During this Truman LDRD project, I studied a collection of nonlinear problems that are of interest to the field of plasma physics. This LDRD report summarizes four main research accomplishments. First, a new statistical model for describing inhomogeneous drift-wave turbulence inter- acting with zonal flows was developed. This new model includes the effects of nonlinear wave-wave collisions, which are expected to change the spectrum of the underlying DW turbulence and therefore the generation of zonal flows. Second, a new mathematical formalism was proposed to systematically apply the non- linear WKB approximation to general field theories, including those often used in fluid dynamics. This formalism represents an interesting tool for studying physical systems that show an explicit scale separation. Third, a weakly nonlinear model was developed to describe the magneto-Rayleigh-Taylor instability. This instability is of paramount importance to understand as it can reduce the performance of magnetic-inertial-fusion (MIF) platforms. The developed models captures the effects of harmonic generation and saturation of the linear growth of the instability. Finally, a framework was proposed for scaling magneto-inertial fusion (MIF) targets to larger pulsed-power drivers. From this framework, a set of scaling rules were derived that conserve the physical regimes of MIF systems when scaling up in peak current. By doing so, deleterious nonlinear processes that affect MIF performance may be kept at bay.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

SU-F-T-369: Validation of Monte-Carlo Beam Model for a Range of Small Fields in Heterogeneous Medium - A Measurement Based Study

Purpose: To validate the Monaco montecorlo beam model for a range of small field in the heterogeneous medium. Methods: A in-house phantom with three different medium of Foam, PMMA and derlin resembling the densities of lung, soft tissue, and bone was used for the study. The field sizes of 8, 16, 24, 32 and 48mm were studied for the validation of montecarlo algorithm using 0.01cc volume ionchamber and gafchromic films. The 6MV photon beam from Elekta Beam modulator was used with 100cm SAD setup. The outputs were measured at the depth of 5, 10 and 20mm in every second medium with 3cm buildup of first medium for the interface of lung-bone, lung-soft tissue, soft tissue-bone, bone-lung and soft tissue-lung. Similarly, the 2D dose analysis with gamma criteria of 2%2mm were done at the same depths using gafchromic film. For all the measurements 10.4×10.4cm were taken as reference to which the other field sizes were compared. Monaco TPSv.3.20 was used to calculate the dose distribution for all the simulated measurement setups. Results: The average maximum difference among the field sizes of 8, 16, 24, 32 and 48mm at the depth of 5mm in second medium with the interface of lung-bone, lung-soft tissue, soft tissue-bone, bone-lung and soft tissue-lung were observed as 1.29±0.14%, 0.49±0.16%, 0.87±0.23%, 0.92±0.11%, 1.01±0.19% respectively. The minimum and maximum variation of dose among different materials for the smallest field size of 8mm were observed as 0.23% and 1.67% respectively. The 2D analysis showed the average gamma passing of 98.9±0.5%. The calculated two-tailed P-value were showed insignificance with values of 0.562 and 0.452 for both ionchamber and film measurements. Conclusion: The accuracy of dose calculation for the small fields in Monaco Montecarlo TPS algorithm was validated in different inhomogeneous medium and found the results were well correlated with measurement data.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

Law of Approach to Saturation in Mn–Zn Ferrite Nanoparticles

In this paper, the law of approach to saturation (LAS) was applied to a series of Mn–Zn ferrite nanoparticles with compositional formula Mn{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4} where x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5 to study the dependence of magnetization, M, on the applied magnetic field, H. Using the statistical parameters, the field range was chosen. The dependence of magnetization on the applied field was studied based upon the output of the statistical parameters for the curve fitted using different forms of LAS, namely, M=M{sub s}[1−(a/H)−(b/(H{sup 2}))]+kH, M=M{sub s}[1−(a/H)−(b/(H{sup 2}))],M=M{sub s}[1−(b/(H{sup 2}))] and M=M{sub s}(1−(1/15)((H{sub A}{sup 2})/(H{sup (1/2)}(H{sup (3/2)}+H{sub R}{sup (3/2)}))))+kH. A critical examination on the output parameters resulted from fitting into different equations, indicates the dependency of magnetization on the applied field as a characteristic of the composition of Mn–Zn ferrites. The statistical parameters, along with physically meaningful fitted parameters, provide knowledge on dependency of magnetization of different compositions of Mn–Zn ferrites over different regions of applied field.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

The Technique of Studying X-Ray Scattering over Wide Temperature Range in an Electric Field

The technique of studying the synchrotron radiation scattering on single crystals over wide temperature range using an original miniature device for applying an electric field to a sample is described. A specific feature of the device is the possibility of its application with various heating and cooling systems. The technique was used at BM01 beamline at the European Synchrotron Radiation Facility (ESRF) for the study of the influence of electric field on the processes of structural transformation in lead zirconate–titanate single crystal with a low titanium concentration. The efficiency of the technique proposed in this work is demonstrated and the results of the preliminary analysis of the results are presented.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS2011

Crew Field Notes: A New Tool for Planetary Surface Exploration

The Desert Research and Technology Studies (DRATS) field tests of 2010 focused on the simultaneous operation of two rovers, a historical first. The complexity and data volume of two rovers operating simultaneously presented significant operational challenges for the on-site Mission Control Center, including the real time science support function. The latter was split into two "tactical" back rooms, one for each rover, that supported the real time traverse activities; in addition, a "strategic" science team convened overnight to synthesize the day's findings, and to conduct the strategic forward planning of the next day or days as detailed in [1, 2]. Current DRATS simulations and operations differ dramatically from those of Apollo, including the most evolved Apollo 15-17 missions, due to the advent of digital technologies. Modern digital still and video cameras, combined with the capability for real time transmission of large volumes of data, including multiple video streams, offer the prospect for the ground based science support room(s) in Mission Control to witness all crew activities in unprecedented detail and in real time. It was not uncommon during DRATS 2010 that each tactical science back room simultaneously received some 4-6 video streams from cameras mounted on the rover or the crews' backpacks. Some of the rover cameras are controllable PZT (pan, zoom, tilt) devices that can be operated by the crews (during extensive drives) or remotely by the back room (during EVAs). Typically, a dedicated "expert" and professional geologist in the tactical back room(s) controls, monitors and analyses a single video stream and provides the findings to the team, commonly supported by screen-saved images. It seems obvious, that the real time comprehension and synthesis of the verbal descriptions, extensive imagery, and other information (e.g. navigation data; time lines etc) flowing into the science support room(s) constitute a fundamental challenge to future mission operations: how can one analyze, comprehend and synthesize -in real time- the enormous data volume coming to the ground? Real time understanding of all data is needed for constructive interaction with the surface crews, and it becomes critical for the strategic forward planning process.

Horz, Friedrich↗
DOE OSTI2018

Features of Relaxation of a Stress Tensor in the Microscopic Volume of Nematic Phase under the Action of a Strong Electric Field

A numerical study of new regimes of reorientation of director field n̂, velocity v, and components of stress tensor σ{sub ij} (ij = x, y, z) of nematic liquid crystal (LC) encapsulated in a rectangular channel under the action of a strong electric field E directed at angle α(∼(π/2)) to the horizontal surfaces bounding the LC channel is proposed. The numerical calculations performed in the framework of nonlinear generalization of the classical Eriksen-Leslie theory have shown that at certain relations between the torques and momenta affecting the unit LC volume and E ≫ E{sub th}, transition periodic structures can emerge during reorientation of n̂, if the corresponding distortion mode has the fastest response, and, thus, suppress all other modes. Rotating domains originating within this process decrease the energy dissipation rate and create more favorable regimes of the director field reorientation, as compared with the uniform rotational displacement.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1979

Solar-Planetary Relationships: Magnetospheric Physics

The quadrennium 1975-1978 was a period of great advance for solar-wind studies, a period that combined exploration of new regions with increased maturity in established fields of study. The Helios, Pioneer, and Voyager spacecraft have been exploring the inner and outer regions of the solar wind. There has been a rebirth of the study of possible relations between solar variability and Earth's climate and weather, stimulated largely by Eddy's investigation of the Maunder Minimum; the solar wind may well prove to be a significant link in solar-terrestrial relations. Unique coronal data from the SKYLAB 1973-1974 mission, in combination with satellite and ground-based observations, provided the basis for identification of coronal holes as the main source of highspeed solar wind. The interplanetary medium has continued to serve as a laboratory for the study of plasma processes that cannot yet be studied in terrestrial laboratories, providing insights of potential importance both for controlled fusion research and for astrophysics. It is ironic that such a productive period, the legacy of many past space missions, was also a time of severely limited opportunity for new space investigations; the outlook for the future is equally austere. Especially regrettable is the dearth of career opportunities for young scientists in this field; comparison of the bibliography of this report with that of its predecessor 4 years ago shows few new names. Despite such problems, research has continued with enthusiasm and much has been learned. The present report will survey selected topics related to the origin, expansion, and acceleration of the solar wind and the plasma physics of the interplanetary medium. Companion reports deal with a number of closely related topics, including the heliocentric distance and latitude variation of the solar wind and its fluctuations topology of the interplanetary magnetic field morphology of solar-wind streams and shocks, sunweather studies, and interplanetary manifestations of type-3 bursts. Of the subjects that fall within the scope of this report, the study of the relationship between coronal holes and solar-wind streams, and the associated revision of our ideas about solar wind acceleration and heating, have had the most impact; hence I review these topics in considerable detail. In addition, I discuss the topics of hydromagnetic waves and turbulence, and interplanetary electrons, as items of particular importance during the past quadrennium.

Barnes, Aaron↗
DOE OSTI2015

Spontaneous excitation of a circularly accelerated atom coupled with vacuum Dirac field fluctuations

We study the spontaneous excitation of a circularly accelerated atom coupled with vacuum Dirac field fluctuations by separately calculating the contribution to the excitation rate of vacuum fluctuations and a cross term which involves both vacuum fluctuations and radiation reaction, and demonstrate that although the spontaneous excitation for the atom in its ground state would occur in vacuum, such atoms in circular motion do not perceive a pure thermal radiation as their counterparts in linear acceleration do since the transition rates of the atom do not contain the Planckian factor characterizing a thermal bath. We also find that the contribution of the cross term that plays the same role as that of radiation reaction in the scalar and electromagnetic fields cases differs for atoms in circular motion from those in linear acceleration. This suggests that the conclusion drawn for atoms coupled with the scalar and electromagnetic fields that the contribution of radiation reaction to the mean rate of change of atomic energy does not vary as the trajectory of the atom changes from linear acceleration to circular motion is not a general trait that applies to the Dirac field where the role of radiation reaction is played by the cross term. - Highlights: • Spontaneous excitation of a circularly accelerated atom is studied. • The atom interacts with the Dirac field through nonlinear coupling. • A cross term involving vacuum fluctuations and radiation reaction contributes. • The atom in circular motion does not perceive pure thermal radiation. • The contribution of the cross term changes as the atomic trajectory varies.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1974

Research on development of equations for performance trajectory computations

The analytical foundation of the Hamilton-Jacobi theory was investigated for application to space flight problems. A specific problem area is defined as follows: (1) to attempt to use the first order perturbation theory, which has been developed for the motion of a uniaxial satellite in a gravitational field in studying the motion of a triaxial satellite in a gravity field; and (2) also to expand theory for the uniaxial case to higher order.

Harmon, G. R.↗
NASA NTRS1984

Crack tip field and fatigue crack growth in general yielding and low cycle fatigue

Fatigue life consists of crack nucleation and crack propagation periods. Fatigue crack nucleation period is shorter relative to the propagation period at higher stresses. Crack nucleation period of low cycle fatigue might even be shortened by material and fabrication defects and by environmental attack. In these cases, fatigue life is largely crack propagation period. The characteristic crack tip field was studied by the finite element method, and the crack tip field is related to the far field parameters: the deformation work density, and the product of applied stress and applied strain. The cyclic carck growth rates in specimens in general yielding as measured by Solomon are analyzed in terms of J-integral. A generalized crack behavior in terms of delta is developed. The relations between J and the far field parameters and the relation for the general cyclic crack growth behavior are used to analyze fatigue lives of specimens under general-yielding cyclic-load. Fatigue life is related to the applied stress and strain ranges, the deformation work density, crack nucleus size, fracture toughness, fatigue crack growth threshold, Young's modulus, and the cyclic yield stress and strain. The fatigue lives of two aluminum alloys correlate well with the deformation work density as depicted by the derived theory. The general relation is reduced to Coffin-Manson low cycle fatigue law in the high strain region.

Minzhong, Z.↗
NASA NTRS1993

Sheet flow fields on Venus

A survey of flow fields with areas greater than 50,000 sq km revealed fields with sheet-like morphology. These sheet flow fields are distinguished by their relatively uniform backscatter, lack of internal flow structure such as well defined lava streams or channels, absence of flow lobes, and irregular boundaries. Internal flow boundaries are essentially absent in these fields, and as such they cannot usually be divided into separate stratigraphic units or eruptive episodes. This is unlike other flow fields with more digitate morphologies, which are made up of discrete flow lobes, and can usually be divided into several episodes of flow emplacement. Five sheet flow fields were studied so far, and other candidates were found. A flow field associated with Lauma Dorsa is taken as an example and examined in detail.

Lancaster, M. G.↗
NASA NTRS1993

Electric field-mediated processing of polymer blend solutions

Multiphase polymer blends in which the minor phases are oriented in a desired direction may demonstrate unique optical, electrical, and mechanical properties. While morphology development in shear fields was studied extensively, little work has focused on effects of electric fields on phase structure. The use of electric fields for blend morphology modulation with particular attention given to solvent casting of blends in d.c. fields was explored. Both homopolymer blends (average phase sizes of several microns) and diblock copolymer/homopolymer blends (average phase sizes of hundreds of Angstroms) were investigated. Summarized are important observations and conclusions.

Wnek, G. E.↗
DOE OSTI2016

THE EFFECTS OF SPATIAL SMOOTHING ON SOLAR MAGNETIC HELICITY PARAMETERS AND THE HEMISPHERIC HELICITY SIGN RULE

The hemispheric preference for negative/positive helicity to occur in the northern/southern solar hemisphere provides clues to the causes of twisted, flaring magnetic fields. Previous studies on the hemisphere rule may have been affected by seeing from atmospheric turbulence. Using Hinode /SOT-SP data spanning 2006–2013, we studied the effects of two spatial smoothing tests that imitate atmospheric seeing: noise reduction by ignoring pixel values weaker than the estimated noise threshold, and Gaussian spatial smoothing. We studied in detail the effects of atmospheric seeing on the helicity distributions across various field strengths for active regions (ARs) NOAA 11158 and NOAA 11243, in addition to studying the average helicities of 179 ARs with and without smoothing. We found that, rather than changing trends in the helicity distributions, spatial smoothing modified existing trends by reducing random noise and by regressing outliers toward the mean, or removing them altogether. Furthermore, the average helicity parameter values of the 179 ARs did not conform to the hemisphere rule: independent of smoothing, the weak-vertical-field values tended to be negative in both hemispheres, and the strong-vertical-field values tended to be positive, especially in the south. We conclude that spatial smoothing does not significantly affect the overall statistics for space-based data, and thus seeing from atmospheric turbulence seems not to have significantly affected previous studies’ ground-based results on the hemisphere rule.

79 ASTRONOMY AND ASTROPHYSICS↗