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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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NASA NTRS1987

Explorations of electric current system in solar active regions. I - Empirical inferences of the current flows

Techniques to identify sources of electric current systems and their channels of flow in solar active regions are explored. Measured photospheric vector magnetic fields together with high-resolution white-light and H-alpha filtergrams provide the data base to derive the current systems in the photosphere and chromosphere. As an example, the techniques are then applied to infer current systems in AR 2372 in early April 1980.

Ding, Y. J.↗

NASA NTRS1990

Current collection in an anisotropic plasma

A general method is given to derive the current-potential relations in anisotropic plasmas. Orbit limit current is assumed. The collector is a conductive sphere or an infinite cylinder. Any distribution which is an arbitrary function of the velocity vector can be considered as a superposition of many mono-energetic beams whose current-potential relations are known. The results for two typical pitch angle distributions are derived and discussed in detail. The general properties of the current potential relations are very similar to that of a Maxwellian plasma except for an effective temperature which varies with the angle between the magnetic field and the charging surface. The conclusions are meaningful to generalized geometries.

Li, Wei-Wei↗

NASA NTRS1992

Current collection in an anisotropic collisionless plasma

Li, Wei-Wei↗

NASA NTRS1981

On the presence of electric currents in the solar atmosphere. I - A theoretical framework

The general magnetic field above the solar photosphere is divided by an elementary analysis based on Ampere's law into two parts: a potential field due to electric currents below the photosphere and a field produced by electric currents above the photosphere combined with the induced mirror currents. The latter, by symmetry, has a set of field lines lying in the plane taken to be the photosphere which may be constructed from given vector magnetograph measurements. These field lines also represent all the information on the electric currents above the photosphere that a magnetograph can provide. Theoretical illustrations are given, and implications for data analysis are discussed.

Hagyard, M.↗

NASA NTRS1994

Euler potentials of current-free fields expressed in spherical harmonics

Given a magnetic field B = -del(vector differential operator)(sub gamma) with gamma expanded in spherical harmonics, it is shown that analytic Euler potentials may be derived for B if gamma is asymmetrical but contains only the contribution of a single index n. This work generalizes a result for sectorial harmonics with n = m, derived by Willis and Gardiner (1988).

Stern, David P.↗

NASA NTRS1999

Summary of Work for Joint Research Interchanges with DARWIN Integrated Product Team 1998

The intent of Stanford University's SciVis group is to develop technologies that enabled comparative analysis and visualization techniques for simulated and experimental flow fields. These techniques would then be made available under the Joint Research Interchange for potential injection into the DARWIN Workspace Environment (DWE). In the past, we have focused on techniques that exploited feature based comparisons such as shock and vortex extractions. Our current research effort focuses on finding a quantitative comparison of general vector fields based on topological features. Since the method relies on topological information, grid matching and vector alignment is not needed in the comparison. This is often a problem with many data comparison techniques. In addition, since only topology based information is stored and compared for each field, there is a significant compression of information that enables large databases to be quickly searched. This report will briefly (1) describe current technologies in the area of comparison techniques, (2) will describe the theory of our new method and finally (3) summarize a few of the results.

Hesselink, Lambertus↗

NASA NTRS1999

Summary of Work for Joint Research Interchanges with DARWIN Integrated Product Team

The intent of Stanford University's SciVis group is to develop technologies that enabled comparative analysis and visualization techniques for simulated and experimental flow fields. These techniques would then be made available un- der the Joint Research Interchange for potential injection into the DARWIN Workspace Environment (DWE). In the past, we have focused on techniques that exploited feature based comparisons such as shock and vortex extractions. Our current research effort focuses on finding a quantitative comparison of general vector fields based on topological features. Since the method relies on topological information, grid matching an@ vector alignment is not needed in the comparison. This is often a problem with many data comparison techniques. In addition, since only topology based information is stored and compared for each field, there is a significant compression of information that enables large databases to be quickly searched. This report will briefly (1) describe current technologies in the area of comparison techniques, (2) will describe the theory of our new method and finally (3) summarize a few of the results.

Hesselink, Lambertus↗

DOE OSTI2017

Dark matter interpretation of the Fermi -$\mathrm{LAT}$ observation toward the Galactic Center

The center of the Milky Way is predicted to be the brightest region of γ-rays generated by self-annihilating dark matter particles. Excess emission about the Galactic center above predictions made for standard astrophysical processes has been observed in γ-ray data collected by the Fermi Large Area Telescope. It is well described by the square of a Navarro, Frenk, and White dark matter density distribution. Although other interpretations for the excess are plausible, the possibility that it arises from annihilating dark matter is valid. Here in this paper, we characterize the excess emission as annihilating dark matter in the framework of an effective field theory. Here we consider the possibility that the annihilation process is mediated by either pseudoscalar or vector interactions and constrain the coupling strength of these interactions by fitting to the Fermi Large Area Telescope data for energies 1–100 GeV in the 15° × 15° region about the Galactic center using self-consistently derived interstellar emission models and point source lists for the region. The excess persists and its spectral characteristics favor a dark matter particle with a mass in the range approximately from 50 to 190 (10 to 90) GeV and annihilation cross section approximately from 1 × 10 -26 to 4 × 10 -25 (6 × 10 -27 to 2 × 10 -25 ) cm 3 /s for pseudoscalar (vector) interactions. We map these intervals into the corresponding WIMP-neutron scattering cross sections and find that the allowed range lies well below current and projected direct detection constraints for pseudoscalar interactions, but are typically ruled out for vector interactions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2012

Adaptive Sampling using Support Vector Machines

Reliability/safety analysis of stochastic dynamic systems (e.g., nuclear power plants, airplanes, chemical plants) is currently performed through a combination of Event-Tress and Fault-Trees. However, these conventional methods suffer from certain drawbacks: • Timing of events is not explicitly modeled • Ordering of events is preset by the analyst • The modeling of complex accident scenarios is driven by expert-judgment For these reasons, there is currently an increasing interest into the development of dynamic PRA methodologies since they can be used to address the deficiencies of conventional methods listed above.

99 GENERAL AND MISCELLANEOUS↗

NASA NTRS1999

Integrated Computational System for Aerodynamic Steering and Visualization

In February of 1994, an effort from the Fluid Dynamics and Information Sciences Divisions at NASA Ames Research Center with McDonnel Douglas Aerospace Company and Stanford University was initiated to develop, demonstrate, validate and disseminate automated software for numerical aerodynamic simulation. The goal of the initiative was to develop a tri-discipline approach encompassing CFD, Intelligent Systems, and Automated Flow Feature Recognition to improve the utility of CFD in the design cycle. This approach would then be represented through an intelligent computational system which could accept an engineer's definition of a problem and construct an optimal and reliable CFD solution. Stanford University's role focused on developing technologies that advance visualization capabilities for analysis of CFD data, extract specific flow features useful for the design process, and compare CFD data with experimental data. During the years 1995-1997, Stanford University focused on developing techniques in the area of tensor visualization and flow feature extraction. Software libraries were created enabling feature extraction and exploration of tensor fields. As a proof of concept, a prototype system called the Integrated Computational System (ICS) was developed to demonstrate CFD design cycle. The current research effort focuses on finding a quantitative comparison of general vector fields based on topological features. Since the method relies on topological information, grid matching and vector alignment is not needed in the comparison. This is often a problem with many data comparison techniques. In addition, since only topology based information is stored and compared for each field, there is a significant compression of information that enables large databases to be quickly searched. This report will (1) briefly review the technologies developed during 1995-1997 (2) describe current technologies in the area of comparison techniques, (4) describe the theory of our new method researched during the grant year (5) summarize a few of the results and finally (6) discuss work within the last 6 months that are direct extensions from the grant.

Hesselink, Lambertus↗

DOE OSTI2022

Improved Limit on Tensor Currents in the Weak Interaction from Li 8 β Decay

Here, the electroweak interaction in the standard model is described by a pure vector-axial-vector structure, though any Lorentz-invariant component could contribute. In this Letter, we present the most precise measurement of tensor currents in the low-energy regime by examining the $β-\bar{ν}$ correlation of trapped 8 Li ions with the Beta-decay Paul Trap. We find $a_{β\barν}$ = - 0.3325 ± 0.0013 stat ± 0.0019 syst at 1σ for the case of coupling to right-handed neutrinos (C T = -C$^{'}_{T}$), which is consistent with the standard model prediction.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2015

New vector-like fermions and flavor physics

We study renormalizable extensions of the standard model that contain vector-like fermions in a (single) complex representation of the standard model gauge group. There are 11 models where the vector-like fermions Yukawa couple to the standard model fermions via the Higgs field. These models do not introduce additional fine-tunings. They can lead to, and are constrained by, a number of different flavor-changing processes involving leptons and quarks, as well as direct searches. An interesting feature of the models with strongly interacting vector-like fermions is that constraints from neutral meson mixings (apart from CP violation in $ {K}^0-{\overline{K}}^0 $ mixing) are not sensitive to higher scales than other flavor-changing neutral-current processes. We identify order 1/(4πM) 2 (where M is the vector-like fermion mass) one-loop contributions to the coefficients of the four-quark operators for meson mixing, that are not suppressed by standard model quark masses and/or mixing angles.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

NASA NTRS1993

Design of a ZVS PWM inverter for a brushless DC motor in an EMA application

The Component Development Division of the Propulsion Laboratory at Marshall Space Flight Center (MSFC) is currently investigating the use of electromechanical actuators for use in space transportation applications such as Thrust Vector Control (TVC). These high power servomechanisms will require rugged, reliable, and compact power electronic modules capable of modulating several hundred amperes of current at up to 270 Vdc. This paper will discuss the design and implementation of a zero-voltage-switched PWM (Pulse Width Modulation) inverter which operates from a 270 Vdc source at currents up to 100 A.

Bell, J. Brett↗

NASA NTRS1991

Analysis of superconducting electromagnetic finite elements based on a magnetic vector potential variational principle

Electromagnetic finite elements are extended based on a variational principle that uses the electromagnetic four potential as primary variable. The variational principle is extended to include the ability to predict a nonlinear current distribution within a conductor. The extension of this theory is first done on a normal conductor and tested on two different problems. In both problems, the geometry remains the same, but the material properties are different. The geometry is that of a 1-D infinite wire. The first problem is merely a linear control case used to validate the new theory. The second problem is made up of linear conductors with varying conductivities. Both problems perform well and predict current densities that are accurate to within a few ten thousandths of a percent of the exact values. The fourth potential is then removed, leaving only the magnetic vector potential, and the variational principle is further extended to predict magnetic potentials, magnetic fields, the number of charge carriers, and the current densities within a superconductor. The new element produces good results for the mean magnetic field, the vector potential, and the number of superconducting charge carriers despite a relatively high system condition number. The element did not perform well in predicting the current density. Numerical problems inherent to this formulation are explored and possible remedies to produce better current predicting finite elements are presented.

Schuler, James J.↗

DOE OSTI2023

Scoping review of Culex mosquito life history trait heterogeneity in response to temperature

Abstract Background Mosquitoes in the genus Culex are primary vectors in the US for West Nile virus (WNV) and other arboviruses. Climatic drivers such as temperature have differential effects on species-specific changes in mosquito range, distribution, and abundance, posing challenges for population modeling, disease forecasting, and subsequent public health decisions. Understanding these differences in underlying biological dynamics is crucial in the face of climate change. Methods We collected empirical data on thermal response for immature development rate, egg viability, oviposition, survival to adulthood, and adult lifespan for Culex pipiens, Cx. quinquefasciatus, Cx. tarsalis , and Cx. restuans from existing literature according to the PRISMA scoping review guidelines. Results We observed linear relationships with temperature for development rate and lifespan, and nonlinear relationships for survival and egg viability, with underlying variation between species. Optimal ranges and critical minima and maxima also appeared varied. To illustrate how model output can change with experimental input data from individual Culex species, we applied a modified equation for temperature-dependent mosquito type reproduction number for endemic spread of WNV among mosquitoes and observed different effects. Conclusions Current models often input theoretical parameters estimated from a single vector species; we show the need to implement the real-world heterogeneity in thermal response between species and present a useful data resource for researchers working toward that goal. Graphical Abstract

59 BASIC BIOLOGICAL SCIENCES↗

NASA NTRS1981

Japanese Magsat Team. A: Crustal structure near Japan and its Antarctic Station. B: Electric currents and hydromagnetic waves in the ionosphere and the magnetosphere

Efforts continue in compiling tapes which contain vector and scalar data decimated at an interval of 0.5 sec, together with time and position data. A map of the total force field anomaly around Japan was developed which shows a negative magnetic anomaly in the Okhotsk Sea. Examination of vector residuals from the MGST model shows that the total force perturbation is almost ascribable to the perturbation parallel to the main geomagnetic field and that the contribution from the perturbation transverse to the main field to the total force perturbation is negligibly small. The influences of ionospheric current with equatorial electroject and of the magnetospheric field aligned current on the dawn-dusk asymmetry of daily geomagnetic variations are being considered. The total amount of electric current flowing through the plane of the Magsat orbit loop was calculated by direct application of Maxwell's equation. Results show that the total electric current is 1 to 5 ampheres, and the current direction is either sunward or antisunward.

Fukushima, N.↗

NASA NTRS1976

Prediction methods for jet V/STOL propulsion aerodynamics

The current status of prediction methods for propulsive flows and propulsion-induced effects which occur on jet V/STOL aircraft is reviewed. Among the major topics studied are flows in propulsive ducts, propulsion-induced ground and thermal effects, aerodynamic loads induced during V/STOL and transition flight, flow vectoring devices, and thrust augmented ejector and lift-fan studies. The current predictive capability in jet V/STOL propulsion aerodynamics is assessed. Future research needs are identified, with particular reference to activities that can improve the usefulness of prediction methods for jet V/STOL aircraft.

Platzer, M. F.↗

NASA NTRS1971

Rocket-based measurement of Birkeland currents related to an auroral arc and electrojet.

A rocket-borne experiment performed to study currents associated with a quiet auroral arc is discussed. The magnetic field in the vicinity of the arc was measured with a vector magnetometer, while the orientation of the payload was determined with a lunar-aspect sensor. Possible current configurations were inferred by constructing model current systems that reproduced the magnetic field variations measured along the flight path. The data are interpreted in terms of a model current system consisting of a northwestward electrojet and two oppositely directed Birkeland sheet currents, all lying in planes approximately parallel to the auroral arc. The current density integrated through the 16-km thickness of each Birkeland current sheet was found to be roughly 0.16 A/m. The electrojet current was roughly 6000 A.

Park, R. J.↗