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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 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

DIRECT OBSERVATION OF THE TURBULENT emf AND TRANSPORT OF MAGNETIC FIELD IN A LIQUID SODIUM EXPERIMENT

For the first time, we have directly measured the transport of a vector magnetic field by isotropic turbulence in a high Reynolds number liquid metal flow. In analogy with direct measurements of the turbulent Reynolds stress (turbulent viscosity) that governs momentum transport, we have measured the turbulent electromotive force (emf) by simultaneously measuring three components of velocity and magnetic fields, and computed the correlations that lead to mean-field current generation. Furthermore, we show that this turbulent emf tends to oppose and cancel out the local current, acting to increase the effective resistivity of the medium, i.e., it acts as an enhanced magnetic diffusivity. This has important implications for turbulent transport in astrophysical objects, particularly in dynamos and accretion disks.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2012

EVOLUTION OF RELATIVE MAGNETIC HELICITY AND CURRENT HELICITY IN NOAA ACTIVE REGION 11158

Both magnetic and current helicities are crucial ingredients for describing the complexity of active-region magnetic structure. In this Letter, we present the temporal evolution of these helicities contained in NOAA active region 11158 during five days from 2011 February 12 to 16. The photospheric vector magnetograms of the Helioseismic and Magnetic Imager on board the Solar Dynamic Observatory were used as the boundary conditions for the coronal field extrapolation under the assumption of nonlinear force-free field, from which we calculated both relative magnetic helicity and current helicity. We construct a time-altitude diagram in which altitude distribution of the magnitude of current helicity density is displayed as a function of time. This diagram clearly shows a pattern of upwardly propagating current helicity density over two days prior to the X2.2 flare on February 15 with an average propagation speed of {approx}36 m s{sup -1}. The propagation is synchronous with the emergence of magnetic flux into the photosphere, and indicative of a gradual energy buildup for the X2.2 flare. The time profile of the relative magnetic helicity shows a monotonically increasing trend most of the time, but a pattern of increasing and decreasing magnetic helicity above the monotonic variation appears prior to each of two major flares, M6.6 and X2.2, respectively. The physics underlying this bump pattern is not fully understood. However, the fact that this pattern is apparent in the magnetic helicity evolution but not in the magnetic flux evolution makes it a useful indicator in forecasting major flares.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

A theory of R(D*, D) anomaly with right-handed currents

We present an ultraviolet complete theory for the R ( D * ) and R ( D ) anomaly in terms of a low mass W ± R gauge boson of a class of left-right symmetric models. These models, which are based on the gauge symmetry SU(3) c × SU(2) L × SU(2) R × U(1) B - L , utilize vector-like fermions to generate quark and lepton masses via a universal seesaw mechanism. A parity symmetric version as well as an asymmetric version are studied. A light sterile neutrino emerges naturally in this setup, which allows for new decay modes of B -meson via right-handed currents. We show that these models can explain R ( D * ) and R ( D ) anomaly while being consistent with LHC and LEP data as well as low energy flavor constraints arising from \( {K}_L-{K}_S,\kern0.5em {B}_{d,s}-{\overline{B}}_{d,s},\kern0.5em D-\overline{D} \) mixing, etc., but only for a limited range of the W R mass: 1.2 (1.8) TeV ≤ \( {M}_{W_R} \) ≤ 3 TeV for parity asymmetric (symmetric) Yukawa sectors. The ratio R ( D )/ R ( D * ) is predicted to be ≃ 1.16, which is the same as in the Standard Model. The light sterile neutrinos predicted by the model may be relevant for explaining the MiniBoone and LSND neutrino oscillation results. The parity symmetric version of the model provides a simple solution to the strong CP problem without relying on the axion. It also predicts an isospin singlet top partner with a mass M T = (1.5 - 2.5) TeV.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

On quantum compatibility of counterterm deformations and duality symmetries in $ \mathcal{N}\ge 5 $ supergravities

In N = 5, 6, 8 supergravities there are hidden symmetries of equations of motion, described by duality groups SU(1, 5), SO*(12), E 7(7) respectively. UV divergences and known candidate counterterms violate the deformed duality symmetry current conservation. Extra higher derivative terms in the action are required to restore duality. We study the effect of a two-vector part of the counterterm for $ \mathcal{N}\ge 5 $ supergravities using the universality of the symplectic structure of extended supergravities. We construct a compact form of a deformed action with infinite number of higher derivative terms and restored duality symmetry with deformation parameter λ. We find, in λ 2 approximation, that the SU( N ) symmetry of the deformed theory is restored on shell.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Latest results from GlueX

The GlueX experiment is housed in the newest experimental hall at the Thomas Jefferson National Accelerator Facility in Newport News, Virginia. It was successfully commissioned in 2015 and is in its third year of data taking. GlueX uses a 12 GeV electron beam incident on a diamond radiator, producing a linearly polarized, coherent Bremsstrahlung photon beam. The ultimate goal of GlueX is to search for exotic hybrid mesons (e.g. $q\bar{q}g$), with either exotic or conventional quantum numbers, whose existence, or lack thereof, would allow for the exploration of the gluon-gluon coupling present in QCD through the manifestation of hadrons with gluonic degrees of freedom. Photo-production at these energies is fairly unexplored and the linear beam polarization allows GlueX to discriminate between various production mechanisms which may be an effective way to identify such exotic hybrid mesons. In addition to exotic mesons, GlueX will also be poised to map out the conventional meson spectrum and to study the spectrum of excited vector mesons, which are often poorly understood. Here in these proceedings, we will present an overview of the GlueX experiment, its goals, current physics results, and future plans.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Intertwined spin-orbital coupled orders in the iron-based superconductors

The underdoped phase diagram of the iron-based superconductors exemplifies the complexity common to many correlated materials. Indeed, multiple ordered states that break different symmetries but display comparable transition temperatures are present. Here we argue that such a complexity can be understood within a simple unifying framework. This framework, built to respect the symmetries of the nonsymmorphic space group of the FeAs/Se layer, consists of primary magnetically ordered states and their vestigial phases that intertwine spin and orbital degrees of freedom. All vestigial phases have Ising-like and zero wave-vector order parameters, described in terms of composite spin order and exotic orbital-order patterns such as spin-orbital loop currents, staggered atomic spin-orbit coupling, and emergent Rashba- and Dresselhaus-type spin-orbit interactions. Moreover, they host unusual phenomena, such as the electronematic effect, by which electric fields act as transverse fields to the nematic order parameter, and the ferro-Néel effect, by which a uniform magnetic field induces Néel order. Here, we discuss the experimental implications of our findings to iron-based superconductors and possible extensions to other correlated compounds with similar space groups.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Latest results from GlueX

The GlueX experiment is housed in the newest experimental hall at the Thomas Jefferson National Accelerator Facility in Newport News, Virginia. It was successfully commissioned in 2015 and is in its third year of data taking. GlueX uses a 12 GeV electron beam incident on a diamond radiator, producing a linearly polarized, coherent Bremsstrahlung photon beam. The ultimate goal of GlueX is to search for exotic hybrid mesons (e.g. $q\bar{q}g$), with either exotic or conventional quantum numbers, whose existence, or lack thereof, would allow for the exploration of the gluon-gluon coupling present in QCD through the manifestation of hadrons with gluonic degrees of freedom. Photo-production at these energies is fairly unexplored and the linear beam polarization allows GlueX to discriminate between various production mechanisms which may be an effective way to identify such exotic hybrid mesons. In addition to exotic mesons, GlueX will also be poised to map out the conventional meson spectrum and to study the spectrum of excited vector mesons, which are often poorly understood. Here in these proceedings, we will present an overview of the GlueX experiment, its goals, current physics results, and future plans.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

ANALYTIC PROPERTIES OF FORCE-FREE JETS IN THE KERR SPACETIME—II

We reinvestigate the structure of a steady axisymmetric force-free magnetosphere around a Kerr black hole (BH). The BH magnetosphere structure is governed by a second-order differential equation of A{sub ϕ} depending on two “free” functions Ω and I, where A{sub ϕ} is the ϕ component of the vector potential of the electromagnetic field, Ω is the angular velocity of the magnetic field lines, and I is the poloidal electric current. While the two functions Ω and I are not arbitrarily given, they do need to be self-consistently determined along with the differential equation. Based on the perturbation approach we proposed in paper I, in this paper, we self-consistently sort out two boundary conditions governing Ω and I, and interpret these conditions mathematically and physically. Making use of the boundary conditions, we prove that all magnetic field lines crossing the infinite-redshift surface also penetrate the event horizon. Furthermore, we argue that the BH Meissner effect does not work in a force-free magnetosphere due to the perfect conductivity.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Analytic Properties of Force-free Jets in the Kerr Spacetime. III. Uniform Field Solution

The structure of the steady axisymmetric force-free magnetosphere of a Kerr black hole (BH) is governed by a second-order partial differential equation of A {sub ϕ} depending on two “free” functions Ω(A{sub ϕ}) and I(A{sub ϕ}), where A {sub ϕ} is the ϕ component of the vector potential of the electromagnetic field, Ω is the angular velocity of the magnetic field lines, and I is the poloidal electric current. In this paper, we investigate the solution uniqueness. Taking the asymptotically uniform field as an example, analytic studies imply that there are infinitely many solutions approaching the uniform field at infinity, while only a unique one is found in general relativistic magnetohydrodynamic simulations. To settle the disagreement, we reinvestigate the structure of the governing equation and numerically solve it with given constraint and boundary conditions. We find that the constraint condition (field lines smoothly crossing the light surface) and boundary conditions at the horizon and at infinity are connected via radiation conditions at horizon and at infinity, rather than being independent. With appropriate constraint and boundary conditions, we numerically solve the governing equation and find a unique solution. Contrary to naive expectations, our numerical solution yields a discontinuity in the angular velocity of the field lines and a current sheet along the last field line crossing the event horizon. We also briefly discuss the applicability of the perturbation approach to solving the governing equation.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1985

Analysis of the inflow layer and air-sea interactions in Hurricane Frederic (1979)

The current study is attempting to overcome the problem of uncertain heights of the satellite winds. The effective heights of the satellite wind vectors were determined. Satellite, aircraft, rawinsonde and surface wind measurements were integrated into a three dimensional analysis of the storm in flow layer over water. Similar analyses of the thermodynamic field in the inflow layer were conducted. Diagnostic budget analyses of moisture, sensible heat kinetic energy and momentum in the inflow layer were conducted. Air-sea interactions were also examined.

Frank, W. M.↗
NASA NTRS1983

A study of optimal abstract jamming strategies vs. noncoherent MFSK

The present investigation is concerned with the performance of uncoded MFSK modulation in the presence of arbitrary additive jamming, taking into account the objective to devise robust antijamming strategies. An abstract model is considered, giving attention to the signal strength as a nonnegative real number X, the employment of X as a random variable, its distribution function G(x), the transmitter's strategy G, the jamming noise as an M-dimensional random vector Z, and the error probability. A summary of previous work on the considered problem is provided, and the results of the current study are presented.

Mceliece, R. J.↗
NASA NTRS1987

Surface waves on Uranus' magnetopause

Uranus' magnetosphere has a well-developed, thick magnetopause that was fully traversed twice by Voyager 2, once inbound to the planet and once outbound. This boundary appears to resemble earth's magnetopause in approximate shape and even to the extent of supporting surface waves which were observed on the inbound pass at a distance of 18.3 Uranus radii. There were apparently eight partial transitions from the magnetosheath into the current sheet of the magnetopause at this time, followed by a final complete transition to the magnetosphere. Six of the estimated normal vectors to the local boundary show clear evidence of oscillations in the slope with typical angular excursions, from one partial transition to the next, of about 90 deg. The vectors oscillated approximately in a plane that was severely tilted by about 49 deg with respect to Uranus' orbital plane.

Lepping, R. P.↗
NASA NTRS1989

Lower-hybrid wave generation in an electron beam of finite transverse dimension

The generation of lower-hybrid waves in an inhomogeneous electron beam is examined. Wave amplitudes are invariably limited by the convective nature of the instability. The self-consistent shear of the magnetic-field geometry due to the beam current is limited to the role of dividing the general problem into separate cases according to the relative orientation of the wave vector and direction of inhomogeneity. Moreover, the limiting case of small shear is smoothly connected to the case where shear is altogether negligible. Estimates of the amplification of lower-hybrid waves propagating across the electron beam are made for the various cases.

Crew, G. B.↗
NASA NTRS1989

Electric auxiliary power unit for Shuttle evolution

The Space Shuttle Orbiter currently uses three hydrazine fueled auxiliary power units (APUs) to provide hydraulic power for the vehicle aerodynamic surface controls, main engine thrust vector control, landing gear, steering, and brakes. Electric auxiliary power units have been proposed as possible replacements to the hydrazine auxiliary power units. Along with the potential advantages, this paper describes an Electric APU configuration and addresses the technical issues and risks associated with the subsystem components. Additionally, characteristics of an Electric APU compared to the existing APU and the direction of future study with respect to the Electric APU is suggested.

Meyer, Doug↗
NASA NTRS1993

Probe compensation in cylindrical near-field scanning: A novel simulation methodology

Probe pattern compensation is essential in near-field scanning geometry, where there is a great need to accurately know far-field patterns at wide angular range. This paper focuses on a novel formulation and computer simulation to determine the precise need for and effect of probe compensation in cylindrical near-field scanning. The methodology is applied to a linear test array antenna and the NASA scatterometer radar antenna. The formulation is based on representing the probe by its equivalent tangential magnetic currents. The interaction between the probe equivalent aperture currents and the test antenna fields is obtained with the application of a reciprocity theorem. This allows us to obtain the probe vector output pickup integral which is proportional to the amplitude and phase of the electric field induced in the probe aperture with respect to its position to the test antenna. The integral is evaluated for each probe position on the required sampling point on a cylindrical near-field surface enclosing the antenna. The use of a hypothetical circular-aperture probe with a different radius permits us to derive closed-form expressions for its far-field radiation patterns. These results, together with the probe vector output pickup, allow us to perform computer simulated synthetic measurements. The far-field patterns of the test antenna are formulated based on cylindrical wave expansions of both the probe and test antenna fields. In the limit as the probe radius becomes very small, the probe vector output is the direct response of the near-field at a point, and no probe compensation is needed. Useful results are generated to compare the far-field pattern of the test antenna constructed from the knowledge of the simulated near-field with and without probe pattern compensation and the exact results. These results are important since they clearly illustrate the angular range over which probe compensation is needed. It has been found that a probe with an aperture radius of 0.25(lambda), 0.5(lambda), and 1(lambda) needs a little probe compensation, if any, near the test antenna main beam. In addition, a probe with low directivity may provide a better signal-to-noise ratio than a highly directive one. This is evident in test antenna patterns without probe compensation at wide angles.

Hussein, Ziad A.↗
NASA NTRS2001

Life Testing of the Hollow Cathode Plasma Contactor for the ProSEDS Mission

The Propulsive Small Expendable Deployer System (ProSEDS) mission is designed to provide an on-orbit demonstration of the electrodynamic propulsion capabilities of tethers in space. The ProSEDS experiment will be a secondary payload on a Delta 11 unmanned expendable booster. A 5-km conductive tether is attached to the Delta 11 second stage and collects current from the low Earth orbit (LEO) plasma. A hollow cathode plasma contactor emits the collected electrons from the Delta II, completing the electrical circuit with the ambient plasma. The current flowing through the tether generates thrust based on the Lorentz Force Law. The thrust will be generated opposite to the velocity vector, slowing down the spacecraft and causing it to de-orbit in approximately 14 days compared to the normal 6 months. A 10-km non-conductive tether is between the conductive tether and an endmass containing several scientific instruments. The ProSEDS mission lifetime was set at I day because most of the primary objectives can be met in that time. The extended ProSEDS mission will be for as many days as possible, until the Delta 11 second stage burns up or the tether is severed by a micrometeoroid or space debris particle. The Hollow Cathode Plasma Contactor (HCPC) unit has been designed for a 12-day mission. Because of the science requirements to measure the background ambient plasma, the HCPC must operate on a duty cycle. Later in the ProSEDS mission, the HCPC is operated in a manner to allow charging of the secondary battery. Due to the unusual operating requirements by the ProSEDS mission, a development unit of the HCPC was built for thorough testing. This developmental unit was tested for a simulated ProSEDS mission, with measurements of the ability to start and stop during the duty cycle. These tests also provided valuable data for the ProSEDS software requirements. Qualification tests of the HCPC flight hardware are also discussed.

Vaughn, Jason A.↗
NASA NTRS2010

Decision Engines for Software Analysis Using Satisfiability Modulo Theories Solvers

The area of software analysis, testing and verification is now undergoing a revolution thanks to the use of automated and scalable support for logical methods. A well-recognized premise is that at the core of software analysis engines is invariably a component using logical formulas for describing states and transformations between system states. The process of using this information for discovering and checking program properties (including such important properties as safety and security) amounts to automatic theorem proving. In particular, theorem provers that directly support common software constructs offer a compelling basis. Such provers are commonly called satisfiability modulo theories (SMT) solvers. Z3 is a state-of-the-art SMT solver. It is developed at Microsoft Research. It can be used to check the satisfiability of logical formulas over one or more theories such as arithmetic, bit-vectors, lists, records and arrays. The talk describes some of the technology behind modern SMT solvers, including the solver Z3. Z3 is currently mainly targeted at solving problems that arise in software analysis and verification. It has been applied to various contexts, such as systems for dynamic symbolic simulation (Pex, SAGE, Vigilante), for program verification and extended static checking (Spec#/Boggie, VCC, HAVOC), for software model checking (Yogi, SLAM), model-based design (FORMULA), security protocol code (F7), program run-time analysis and invariant generation (VS3). We will describe how it integrates support for a variety of theories that arise naturally in the context of the applications. There are several new promising avenues and the talk will touch on some of these and the challenges related to SMT solvers. Proceedings

Bjorner, Nikolaj↗
NASA NTRSDate not supplied

U.S. IMERG Status

The U.S. Science Team’s Integrated Multi-satellitE Retrievals for the Global Precipitation Measurement (GPM) mission (IMERG) product provides estimates of surface precipitation rate and related information on a global 0.1° half-hour grid. It is run three times at increasingly longer latency and higher information input to serve different communities. This presentation will briefly summarize the major upgrades included in Version 07. The Goddard Profiling (GPROF) algorithm (applied to passive microwave sensor data from the GPM virtual constellation) and the Combined Radar-Radiometer Algorithm (CORRA) that provide input to IMERG V07 are both improved, and the new Precipitation Estimation from Remotely Sensed Information Using Artificial Neural Networks–Dynamic Infrared Rain Rate (PDIR) algorithm is being applied to infrared data, which employs an additional, warmer infrared temperature threshold than the previous infrared scheme and a deep neural network. V07 has improved bias performance as a result of calibrations that now employ the entire swath widths of CORRA and GPROF GPM Microwave Imager precipitation estimates. As well, time continuity in precipitation features is improved as a result of changes to the Kalman filter that approximately preserve the local histogram of precipitation rates (Scheme for Histogram Adjustment with Ranked Precipitation Estimates in the Neighborhood, or SHARPEN), and that better account for differences in sensor performance. A long-standing bug in the geolocation that shifted grid values 0.1° to the east in the latitude band 70°N-S has been corrected. Other changes in V07 include a hierarchical selection among motion vector sources to address deficiencies in the precipitation propagation near orography, an update to the precipitation phase specification for improved consistency with current inputs, and a renewed effort to implement climatological gauge adjustment to the near-real-time Runs. Early evaluations of V07 IMERG show interesting behavior across the TRMM orbit boost that is highly relevant to the planned orbit boost for the GPM Core observatory.

GPM↗