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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 1,063 records · Page 59
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Multiplicity distributions in interaction models used for cascade simulations

In cascade simulations, conservation of energy is of paramount importance. It is pointed out that it is possible to construct algorithms in which energies of secondaries are chosen from physically correct distributions in such a way as to conserve energy, and give physically correct multiplicity distributions without further adjustment. The resulting non-Poissonian nature of the distribution and the approximate KNO scaling are related to the large fluctuations in the energy available for pion production and to the detailed shape of the inclusive momentum distribution. Two multiparticle production algorithms are described which have these features. One is the algorithm used in the simulation of C jets, the other is for a hadron-nucleus interaction model used in the calculation of muon and neutrino fluxes.

Ellsworth, R. W.↗
NASA NTRS1985

Angular distribution and multiplicity of backward hadrons in hFe interactions at 0.5-5.0 TeV energies (PION Experiment)

Based on the analysis of approximates 5 X 1000 events registered on the PION installation, data are obtained on the angular distribution and multiplicity of particles, flying back into the laboratory coordinate system (LCS) that are identified mainly as hadrons produced in the reactions of hFe yield h prime X type. The inclusively produced hadron energy is 200 MeV. The experimental data are compared to the results of the cumulative particle production in hA processes observed on accelerators at lower energies.

Avakian, V. V.↗
NASA NTRS1985

Excessive production of electron pairs by soft photons in low multiplicity ion interactions

Three multiply charged primary cosmic ray interactions with carbon nuclei are reported, in which the number of materialized electron pairs within a distance of about 0.3 conversion length is larger than predicted from isospin considerations. These are the most energetic (sigma E gamma 4 TeV) of the low multiplicity ( 15 tracks) events observed in the Japanese-American Cooperative Experiment (JACEE-2) emulsion chamber.

Burnett, T. H.↗
NASA NTRS1985

A facility for investigation of multiple hadrons at cosmic-ray energies

An experimental arrangement for studying multiple hadrons produced in high-energy hadron-nucleus interactions is under construction at the university of Turku. The method of investigation is based on the detection of hadrons arriving simultaneously at sea level over an area of a few square meters. The apparatus consists of a hadron spectrometer with position-sensitive detectors in connection with a small air shower array. The position resolution using streamer tube detectors will be about 10 mm. Energy spectra of hadrons or groups of simultaneous hadrons produced at primary energies below 10 to the 16th power eV can be measured in the energy range 1 to 2000 GeV.

Valtonen, E.↗
NASA NTRS1985

Multiple muons in MACRO

An analysis of the multiple muon events in the Monopole Astrophysics and Cosmic Ray Observatory detector was conducted to determine the cosmic ray composition. Particular emphasis is placed on the interesting primary cosmic ray energy region above 2000 TeV/nucleus. An extensive study of muon production in cosmic ray showers has been done. Results were used to parameterize the characteristics of muon penetration into the Earth to the location of a detector.

Heinz, R.↗
NASA NTRS1984

The effects of the diffuse radiation fields due to multiple scattering and thermal reradiation by dust on the dynamics and thermodynamics of a dusty cometary atmosphere

A self-consistent model of a dirty, clathrate cometary nucleus is extended to account for diffuse radiation fields caused by multiple scattering and thermal reradiation of the solar continuum by dust. The model is configured to fit conditions expected for the various spacecraft which will encounter Halley's comet at 0.89 AU. The atmosphere is assumed a chemically reactive dust-gas mixture in quasi-steady spherically symmetric expansion. The effect of electron-neutral ion collisions is accounted for, along with rate constants of the various species of clathrate ice particles and radiative transfer of the solar input in the UV, visible and near-IR intervals. The opacity of the circumnuclear dust is projected to be an order of magnitude greater than previous estimates, which severely impacts the potential visibility of the nucleus to the cameras of the flyby satellites.

Marconi, M. L.↗
NASA NTRS1984

A multiple type-II burst associated with a coronal transient and its MHD simulation

A large coronal transient took place on May 8, 1981. The transient was related to an M7.7/2B flare and was associated with at least two coronal type-II bursts. The velocities of the type-II bursts were in the range 1100-1800 km/s, in excess of the transient velocity of 1000 km/s. Two dimensional positions of the type-II radio sources are available from both the Clark Lake and the Culgoora Radio Observatories. Two dimensional MHD simulations of the event are carried out, taking into account the observed velocity, position, and size of the type-II bursts. The multiple shocks observed during the event and their interaction are simulated, and results of the simulation are discussed.

Gergely, T. E.↗
NASA NTRS1983

Weighted least squares formulas for multiple Doppler radar analysis

An algorithm is developed for the analysis of multiple Doppler radar data in meteorological applications. The algorithm is based on the least squares linear solutions for the variable parameters of a local particle velocity field. The computational sequence for the algorithm is described, and some factors influencing the covariance of Doppler measurement errors are discussed.

Wilson, F. W., Jr.↗
NASA NTRS1985

Molecular beam epitaxial growth and transmission electron microscopy studies of thin GaAs/InAs(100) multiple quantum well structures

GaAs/InAs(100) multiple interface structures involving 7.4 percent lattice mismatch have been fabricated via molecular beam epitaxy and examined via transmission electron microscopy. It is found that high-quality, dislocation-free interfaces involving such high lattice mismatch can indeed be experimentally realized for very thin layers provided proper care is given to achieve a balance between the growth kinetics and the thermodynamics leading to the equilibrium ground state of the strained layer. The compressive strain is homogeneously accommodated and a tetragonal distortion is induced in the InAs layer with a perpendicular lattice constant in close agreement with that expected on the basis of the continuum theory and elastic constants of bulk InAs.

Grunthaner, F. J.↗
NASA NTRS1985

Propagation mechanism of daytime Pc 3-4 pulsations observed at synchronous orbit and multiple ground-based stations

Observational data obtained during the last two decades show that the amplitude of daytime Pc 3-4 magnetic pulsations is controlled by the solar wind conditions. The high degree of correlation between the solar wind parameters and Pc 3-4 pulsations in the dayside magnetosphere suggests that the ultimate cause of the daytime Pc 3-4 pulsations must be the interaction of the solar wind with the earth's magnetosphere. The present paper is concerned with details regarding the control of the properties of the Pc 3-4 pulsations by the solar wind parameters, taking into account observations made at multiple ground-based stations. It is attempted to establish the relation between the daytime Pc 3-4 pulsations at the ground stations and the compressional Pc 3-4 waves in the magnetosphere. Attention is given to the most probable propagation mechanism of the daytime Pc 3-4 pulsations in the magnetosphere.

Yumoto, K.↗
NASA NTRS1985

Multiple Raman up-conversion of radiation from pre-existing Langmuir turbulence

Little is known regarding the mechanisms involved in the production of radiation at frequencies which are much higher than the maximum plasma frequency in nonmagnetic plasmas. It is pointed out that radiation at high multiples of the plasma frequency has been observed in laser-pellet experiments, in relativistic beam-plasma interactions, and in low-energy beam-plasma interactions. Radiation at twice the plasma frequency can be produced by coalescence of two Langmuir waves. Another approach is based on radiation near the plasma frequency or its second harmonic, produced by instability or by external sources. Raman scatter from preexisting Langmuir turbulence is permitted repeatedly. At each step such scattering will produce frequency upshifts (anti-Stokes process) and downshifts (Stokes process). The present paper is concerned with this process. Attention is given to equilibrium spectra, analytic approximations, laser-plasma interaction and coherent radiation from relativistic electron beams.

Russell, D.↗
NASA NTRS1985

Vortex modeling of single and multiple dilution jet mixing in a crossflow

An analytical model for the behavior of normally injected jets in a crossflow is developed and applied to fluids of differing densities. Central to the model are the dynamics of the vortex pair structure associated with the local jet cross-section and the entrainment of crossflow by jet fluid. Two specific cases are modeled: one involving a single dilution jet in a crossflow, in which trajectories are found to scale primarily with jet-to-crossflow momentum ratio, and the other involving a series of spanwise jets injected into a crossflow, which indicates scaling with momentum ratio and with the spacing-to-orifice-diameter ratio. In the case of multiple jet penetration, however, merging of the jets into an approximately two-dimensional jet downstream of injection is observed for low spacing-to-diameter ratios.

Karagozian, A. R.↗
NASA NTRS1985

A time-accurate multiple-grid algorithm

A time-accurate multiple-grid algorithm is described. The algorithm allows one to take much larger time steps with an explicit time-marching scheme than would otherwise be the case. Sample calculations of a scalar advection equation and the Euler equations for an oscillating airfoil are shown. For the oscillating airfoil, time steps an order of magnitude larger than the single-grid algorithm are possible.

Jespersen, D. C.↗
NASA NTRS1985

Operating Characteristics of the Multiple Critical Venturi System and Secondary Calibration Nozzles Used for Weight-Flow Measurements in the Langley 16-Foot Transonic Tunnel

An investigation has been conducted in the Langley 16 Foot Transonic Tunnel to determine the weight flow measurement characteristics of a multiple critical Venturi system and the nozzle discharge coefficient characteristics of a series of convergent calibration nozzles. The effects on model discharge coefficient of nozzle throat area, model choke plate open area, nozzle pressure ratio, jet total temperature, and number and combination of operating Venturis were investigated. Tests were conducted at static conditions (tunnel wind off) at nozzle pressure ratios from 1.3 to 7.0.

Berrier, B. L.↗
NASA NTRS1985

An asymptotic theory for the interference of large aspect ratio swept wings and multiple propeller slipstreams

This paper presents an asymptotic method for the analysis of the interference of multiple tractor propeller slipstream with large aspect ratio swept wings. It is assumed that the height of the slipstream is of the order of the wing chord and its spanwise extent is of the order of the wing span. Three different flow regions are identified by employing different stretching transformations. Asymptotic expansions are made in each of the three regions, using the chord to span ratio as the small expansion parameter. The details of the nonuniform flow in the slipstream enter into the wing sectional analysis. In the outer limit, the wing shrinks to a swept lifting line, and the slipstream reduces to a thin sheet of jet carrying the momentum gain from the propeller. The curvature of this jet sheet results in a pressure difference which is represented by a vortex sheet. The governing equations are solved by discretization. Several examples are considered for which experimental data are available. Comparison of the present results with the experimental data as well as other numerical solutions showed generally good agreement.

Prabhu, R. K.↗