ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • ASTROPHYSICS  (578)
  • FLUID MECHANICS AND HEAT TRANSFER  (331)
  • 2015-2019
  • 1980-1984  (905)
  • 1970-1974
  • 1955-1959  (4)
  • 1925-1929
  • 1983  (905)
  • 1957  (4)
Collection
Keywords
Years
  • 2015-2019
  • 1980-1984  (905)
  • 1970-1974
  • 1955-1959  (4)
  • 1925-1929
Year
  • 1
    facet.materialart.
    Unknown
    Solution adaptive grid generation (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Langley Research Center, Theoretical Aerodynamics Contractors' Workshop, Volume 2; p 651-68
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 2
    facet.materialart.
    Unknown
    Navier-Stokes solution for quasi-three dimensional flow (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Langley Research Center, Theoretical Aerodynamics Contractors' Workshop, Volume 1; p 329-33
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 3
    facet.materialart.
    Unknown
    Vectorized, implicit Navier-Stokes solver for 2-D incompressible flows (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Langley Research Center, Theoretical Aerodynamics Contractors' Workshop, Volume 1; p 273-31
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 4
    facet.materialart.
    Unknown
    Clebsch velocity decomposition for rotational conical flows (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Langley Research Center, Theoretical Aerodynamics Contractors' Workshop, Volume 1; p 183-19
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 5
    facet.materialart.
    Unknown
    Influence of convection on the growth of crystals from solution (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: This is a review of the influence of convection on the growth of crystals from solution. The growth rate is increased by convection up to the point where interface kinetics becomes rate controlling. Compositional inhomogeneity and morphological instability (inclusion formation) are probably worse for gentle convection than for either no convection or for vigorous stirring. Stirring, particularly of crystal suspensions, can cause an orders of magnitude increase in the rate of formation of new crystals. This is called 'secondary nucleation'.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Crystal Growth (ISSN 0022-0248); 65; 133-142
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 6
    facet.materialart.
    Unknown
    X-ray spectra of young supernova remnants (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Einstein solid-state-spectrometer (SSS) spectra are presented for the Crab Nebula, Cas A, SN 1006, the Tycho SNR, and the Kepler SNR. The history of X-ray observations of SNRs is reviewed; the SSS instrument is briefly characterized; a reduction technique which accounts for all background sources in the 0.5-4.5-keV band is applied; and the physical models of SNRs constructed to reproduce the refined spectra are discussed. The limitations of the modeling methods and the need for further observations, especially of localized regions, are indicated.
    Keywords: ASTROPHYSICS
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 7
    facet.materialart.
    Unknown
    Magnetic topology and the heating of extended chromospheres (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: New data indicate that red giants are surrounded by geometrically thick chromospheres of several stellar radii extent. Such chromospheres occur among stars which apparently lack coronae. Maintenance of this extended warm region may require non-compressional wave heating of a magnetic character, and this may provide a crucial clue to the mechanism of rapid mass loss from red giant stars.
    Keywords: ASTROPHYSICS
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 8
    facet.materialart.
    Unknown
    A note on the oxygen gradient in NGC 628 (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The Kitt Peak 2.1-m telescope and Intensified Image Dissector Scanner have been used to gather spectrophotometric data in the 3600-5200 A spectral region for five H II regions in the spiral galaxy NGC 628. The Pagel et al (1979) technique was then applied to determine the relative number abundances of O to H in each of the H II regions. An examination of the abundance values obtained as a function of the radial coordinate yields an O gradient of -0.05 + or - 0.03 dex/kpc.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 95; 986-988
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 9
    facet.materialart.
    Unknown
    The production of turbulent stress in a shear flow by irrotational fluctuations (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Attention is given to the way in which external turbulence affects an initially turbulence-free region in which there is a mean velocity gradient. External turbulence induces irrotational fluctuations in the sheared region which interact with the shear to produce rotational velocity fluctuations and mean Reynolds stresses. Since the actual front between the initial external turbulence and the shear flow is a randomly contorted surface, the turbulence near the front is intermittent, and is presently included in the form of a simple statistical model. In wind tunnel tests, turbulent shear stress was found to grow from zero to significant values in the interaction region. Observed stress magnitude and extent agrees with predictions, and it is concluded that turbulent stresses can be produced by irrotational fluctuations in a region of mean shear.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Fluid Mechanics (ISSN 0022-1120); 137; 307-329
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 10
    facet.materialart.
    Unknown
    Viscous thermocapillary convection at high Marangoni number (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: A liquid, contained in a quarter plane, undergoes steady motion due to thermocapillary forcing on its upper boundary, a free surface separating the liquid from a passive gas. The rigid vertical sidewall has a strip whose temperature is elevated compared with the liquid at infinity. A boudnary-layer analysis is performed that is valid for large Marangoni numbers M and Prandtl numbers P. It is found that the Nusselt number N for the horizontal heat transport satisfies N proportional to min (M to the 1 2/7/power, M to the 1 1/5/power, M to the 1 1/10/power) Generalizations are discussed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Fluid Mechanics (ISSN 0022-1120); 135; 175-188
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 11
    facet.materialart.
    Unknown
    Testing for a cosmological influence on local physics using atomic and gravitational clocks (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The existence of a possible influence of the large-scale structure of the universe on local physics is discussed. A particular realization of such an influence is discussed in terms of the behavior in time of atomic and gravitational clocks. Two natural categories of metric theories embodying a cosmic infuence exist. The first category has geodesic equations of motion in atomic units, while the second category has geodesic equations of motion in gravitational units. Equations of motion for test bodies are derived for both categories of theories in the appropriate parametrized post-Newtonian limit and are applied to the Solar System. Ranging data to the Viking lander on Mars are of sufficient precision to reveal (1) if such a cosmological influence exists at the level of Hubble's constant, and (2) which category of theories is appropriate for a descripton of the phenomenon.
    Keywords: ASTROPHYSICS
    Type: Physical Review D - Particles and Fields, 3rd Series (ISSN 0556-2821); 28; 1822-182
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 12
    facet.materialart.
    Unknown
    Observations of NGC 7027 from 5.2 to 7.5 microns - The detection of Ni II and additional dust features (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: NGC 7027 was observed with a multichannel grating spectrometer from 5.2 to 7.5 microns at a spectral resolving power of 120-200. Two new dust emission features are resolved at 5.62 and 6.95 microns, and for the first time the Ni II fine-structure line at 6.64 microns is detected. It is shown that a single molecular dust constituent might account for six of the nine observed dust features between 2 and 14 microns. The strength of the Ni II line indicates either that Ni is not depleted in the neutral gas, or that the line is formed at high density.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 274; 666-670
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 13
    facet.materialart.
    Unknown
    A new calibration of the extragalactic distance scale using Cepheids and RR Lyrae stars (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Visual absolute magnitudes of classical Cepheids, metal-poor RR Lyrae stars and short-period type II Cepheids have been determined with very high precision by combining a large number of old and new astrophysical data. Five independent methods (four observational and one theoretical) have been successfully used: (1) secular and statistical parallaxes; (2) moving-group parallaxes; (3) cluster main-sequence fitting; (4) the Baade-Wesselink method and its modifications; and (5) light-curve and velocity-curve fitting (the theoretical method). With these five adopted methods, the zero point of the galactic and extragalactic distance scale can be set on a relatively firm and self-consistent basis. Classical Cepheids and RR Lyrae stars now provide essentially identical distances to nearby galaxies: the distance modulus to the Large Magellanic Cloud is 18.5 and to the Small Magellanic Cloud is 18.8, both with an uncertainty of 0.1. The distance to the center of our Galaxy is 8.6 plus or minus 0.5 kiloparsecs. The major uncertainty in these values lies in the correction for interstellar extinction.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 274; 20-30
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 14
    facet.materialart.
    Unknown
    On the line profile coefficient for stimulated emission (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: It is pointed out that the line profile coefficients for spontaneous and stimulated emission are identical in low-intensity radiation fields. In more intense radiation fields, however, the stimulated emission profiles in the radiative transfer equation and in the rate equations for the atomic level populations may differ from each other, owing to their different physical nature. A seeming discrepancy between the stimulated emission profiles of the usual semi-classical aproach and a recent quantum mechanical approach by Cooper et al. (1982), which should also be valid for intense 'broadband' fields, is discussed and shown to have negligible consequences for low-intensity radiation fields.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 127; 1, Oc; 224-226
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 15
    facet.materialart.
    Unknown
    Observational tests of baryon symmetric cosmology (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Observational evidence for Baryon symmetric (matter/antimatter) cosmology and future observational tests are reviewed. The most significant consequences of Baryon symmetric cosmology lie in the prediction of an observable cosmic background of gamma radiation from the decay of Pi(O)-mesons produced in nucleon-antinucleon annihilations. Equations for the prediction of the gamma ray background spectrum for the case of high redshifts are presented. The theoretical and observational plots of the background spectrum are shown to be in good agreement. Measurements of cosmic ray antiprotons and the use of high energy neutrino astronomy to look for antimatter elsewhere in the universe are also addressed. Previously announced in STAR as N83-10996
    Keywords: ASTROPHYSICS
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 16
    facet.materialart.
    Unknown
    Stagnation-point ablation of carbonaceous flat disks. II Experiment (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Six flat-disk models made of carbon-carbon and carbon-phenolic materials were launched in an argon-filled track-range facility to test ablation characteristics in a radiation-dominated, massive-blowing environment. The shock standoff distances deduced from the shadowgraphs agree with theoretical predictions during the earlier portion of the flight, while the wall temperatures determined by the image-converter photographs agree with predictions during the later portion. The measured surface recessions exceed the calculated values by about 60 percent for carbon-phenolic and 30 percent for carbon-carbon. The discrepancies are attributed to spallation. The measured char thicknesses agree with theoretical predictions.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA Journal (ISSN 0001-1452); 21; 1748-175
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 17
    facet.materialart.
    Unknown
    Continuation in a parameter - Experience with viscous and free surface flows (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The results of modifications in continuation methods applied to obtain solutions to the Navier-Stokes systems of equations for incompressible, two-dimensional, steady flows are reported. It is shown that parameter continuation permits prediction of accurate, initial estimates for iterative processing of nonlinear finite difference and finite element equations of motions. The new parameter steps are derived from values of the preceding parameter steps. The accuracy of the estimates is ensured with appropriate choices of the step size. The continuation predictor/iterative corrector is demonstrated to trace the branches of parameter space along which steady flow states are found, and techniques are available for tracing multiply branching paths. The techniques are applied to solving the Navier-Stokes equations for flow through a rotating square channel, the formation of a falling liquid curtain, and gyrostatic equilibria of rotating cylindrical drops.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 18
    facet.materialart.
    Unknown
    Modeling of transient two-component flow using a four-point implicit method (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The four-point, centered implicit scheme that is extensively used in open channel flow simulation is shown to be applicable to rapid and slow pressure transient problems in conduits with nearly single phase and two-phase flows. It is only necessary to choose the proper weighting factor value, theta, of the Courant number. For rapid pressure transients such as waterhammer, the implicit method can yield reasonable results with limited numerical dispersion and attenuation if theta is only slightly greater than the critical value of 0.5. For slower pressure gradients in single and two-phase flows, reasonable numerical solutions may be achieved for Courant number values as high as 20.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 19
    facet.materialart.
    Unknown
    Interacting binary stars - Freaks or rosetta stones (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Attention is given to semidetached binaries of the Algol type and to related interacting systems, such as Beta Lyrae and the W Serpentis stars. A brief description is given of observational problems. The basic properties of the Algol variables are satisfactorily explained by means of evolutionary models that assume considerable mass transfer between the components. It is pointed out that ultraviolet spectra obtained with the IUE satellite corroborate the view that the present subgiant secondary component was initially the more massive star and that it has been stripped of a large fraction of its mass so that the deep layers affected by CNO processing are now denuded. It is believed that the present-day 'classical' Algols must have undergone a phase of rapid mass transfer in the past and that Beta Lyrae and the W Serpentis stars are probably closer to that stage than ordinary Algols. Around the accreting star a complex structure is formed, and an induced stellar wind may blow a large part of the transferred matter out of the system.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society of Canada, Journal (ISSN 0035-872X); 77; 283-304
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 20
    facet.materialart.
    Unknown
    The production of turbulent stress in a shear flow by irrotational fluctuations (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: This paper examines, both theoretically and experimentally, the effect produced by irrotational fluctuations, associated with a nearby turbulent field, in a region where the turbulence is initially very low but where there is a mean shear. Calculations are based on rapid distortion theory and experiments use linearized hot wire anemometers in an open circuit wind tunnel. Turbulent shear stress is observed to grow from zero to significant values in the interaction region. The magnitude and extent of this observed shear stress agree reasonably well with predictions of the analysis, when intermittency effects are included. It is concluded that turbulent stresses can be produced by irrotational fluctuations in a region of mean shear and that this effect can be estimated using rapid distortion theory if the overall strain ratio is not large.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 21
    facet.materialart.
    Unknown
    What causes the buoyancy reversal in compressible convection? (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The problem posed by the existence of a negative buoyancy work region at the top of cellular type convection in a deeply stratified superadiabatic layer (Massaguer and Zahn, 1980) is addressed. It is approached by studying two-dimensional cellular compressible convection with different physical parameters. The results suggest that a large viscosity, together with density stratification, is responsible for the buoyancy reversal. The numerical results obtained are analyzed. It is pointed out, however, that in an astrophysical situation a fluid involved in convection will generally have very small viscosity. It is therefore thought unlikely that buoyancy reversal occurs in this way.
    Keywords: ASTROPHYSICS
    Type: Astrophysics and Space Science (ISSN 0004-640X); 95; 2, Se; 453-457
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 22
    facet.materialart.
    Unknown
    On a vibronic origin for the diffuse band spectrum (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Duley (1982) has proposed that many of the diffuse interstellar bands in the wavelength interval 542-677 nm arise from vibronic transitions of Cr (3+) ions in MgO grains. No explanation has been offered for the fact that as many as 85 of the possible 108 transitions of this system have not been observed in the interstellar medium. Moreover, the relative intensities of the diffuse bands which are observed appear to be inconsistent with their assignment. It is therefore concluded that this model is not consistent with the observations.
    Keywords: ASTROPHYSICS
    Type: Astrophysics and Space Science (ISSN 0004-640X); 95; 1, Se
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 23
    facet.materialart.
    Unknown
    A note on the composition and structure of interstellar grains (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The plausibility of relatively pure diatomic oxide crystals forming in the expanding atmospheres of cool stars is commented on, and the likelihood of SiO grains condensing is discussed on the basis of laboratory nucleation experiments. Results of annealing experiments are used to consider the further evolution of silicon oxide and silicate grains. The evidence shows that SiO solids form only when SiO condenses directly onto surfaces, and that the probability of pure crystalline SiO grains forming is rather small.
    Keywords: ASTROPHYSICS
    Type: Astrophysics and Space Science (ISSN 0004-640X); 95; 1, Se
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 24
    facet.materialart.
    Unknown
    Planetary nebulae and stellar evolution (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Newly defined characteristics of planetary nebulae (PN) derived from analysis of a photometric survey of 57 PN are reported. The data were combined with measurements of 27 other PN made since 1918 and were found to indicate core masses ranging from 0.55-1.0 solar mass. N/O elemental abundance ratios observed were correlated with the planetary nuclei masses, and were in direct proportion. IUE data on PN that overlapped a large part of the survey indicated that the PN in the galactic disk are more massive than PN in the halo. It is suggested that PN evolve into white dwarfs, a hypothesis supported by astrometric solutions for three nearby visual binaries featuring white dwarfs with well-determined masses. It is noted, however, that PN with masses exceeding one solar mass have been sighted in the Magellanic Clouds.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 305; 670
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 25
    facet.materialart.
    Unknown
    A modified Dodge algorithm for the parabolized Navier-Stokes equations and compressible duct flows (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: A revised version of Dodge's split-velocity method for numerical calculation of compressible duct flow was developed. The revision incorporates balancing of mass flow rates on each marching step in order to maintain front-to-back continuity during the calculation. The (checkerboard) zebra algorithm is applied to solution of the three dimensional continuity equation in conservative form. A second-order A-stable linear multistep method is employed in effecting a marching solution of the parabolized momentum equations. A checkerboard iteration is used to solve the resulting implicit nonlinear systems of finite-difference equations which govern stepwise transition. Qualitative agreement with analytical predictions and experimental results was obtained for some flows with well-known solutions. Previously announced in STAR as N82-16363
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: International Journal for Numerical Methods in Fluids (ISSN 0271-2091); 3; 493-506
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 26
    facet.materialart.
    Unknown
    Two new possible planetary nebulae (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Two new possible planetary nebulae have been identified using the Parker, Gull, and Kirshner (1979) emission-line survey of the galactic plane. Both objects exhibit very strong forbidden O III lambda 5007 line emission, a symmetrical morphology, and a faint blue central star.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 95; 614-618
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 27
    facet.materialart.
    Unknown
    Ultraviolet observations of M1-2 (= VV 8) (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: First IUE spectrograms of the peculiar emission-line object M1-2 (= VV 8) are presented. In the wavelength region 1150-3200 A this object is characterized by emission lines superposed on a moderately strong continuum. Some ultraviolet and optical properties of M1-2 are discussed in the context of symbiotic stars and protoplanetary and planetary nebulae. An E(B-V) extinction of 0.37 mag is obtained from the ratio of the He II flux at 1640 and 4686 A and is compared with values derived from other parameters. The ultraviolet observations suggest that M1-2 is a young, high-density planetary nebula of excitation class 5 or 6 with characteristics similar to IC 4997.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 275; 628-635
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 28
    facet.materialart.
    Unknown
    The origin of the Gum nebula (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Obsrvations and theoretical investigations of the Gum nebula (GN) since about 1971 are reviewed. Direct observations of the GN, the Vela X supernova remnant (SNR), the Vela pulsar, and other stars in or near the GN are discussed with those of related phenomena such as the radio loops and known SNRs; the emphasis is on studies of the interstellar absorption lines, the evidence for hot gas in the GN, and the extended diffuse emission. The four basic models proposed for the GN are considered: a fossil Stromgren sphere, an old SNR, an H II region, or a superbubble. The GN physical parameters predicted by each model are listed in a table and compared. A minimum explanation which attributes the 36 x 36-deg filamentary structure and the 125-pc radius structure to the action of the stellar winds from Zeta Pup and Gamma-2 Vel (and perhaps the effect of a Vel X supernova explosion 20,000 years ago) is found most appropriate, at least until the questions of the net expansion rate of the GN (about 20 km/sec or about zero?) and the existence of the diffuse emission beyond the filamentary structure are resolved by observations.
    Keywords: ASTROPHYSICS
    Type: Comments on Modern Physics, Part C - Comments on Astrophysics (ISSN 0146-2970); 10; 1-14
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 29
    facet.materialart.
    Unknown
    Electron velocity distributions near interplantary shocks (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Previous work on electron heating mechanisms operating at the supercritical earth's bow shock is extended to the generally lower Mach number interplanetary shocks. This is done by studying electron velocity distributions observed both upstream and downstream of interplanetary shocks observed by ISEE 3 between August 1978 and December 1979. It is found that perpendicular heating accompanied by little or no parallel heating occurs at the weaker shocks but that parallel heating is dominant for the stronger shocks. When perpendicular heating is dominant, downstream velocity distributions are for the most part Gaussian at low energies (core) and Lorentzian at high energies (halo). When parallel heating is dominant, however, these distributions are flat-topped at low energies, having power law extensions to higher energies. At the weaker shocks, the observations are consistent with electron heating resulting from conservation of the magnetic moment, whereas at the stronger shocks the heating is quite similar to that observed at the earth's bow shock.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 88; 9949-995
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 30
    facet.materialart.
    Unknown
    Sharp shortward-shifted features in the spectra of O subdwarfs (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Preliminary inspection of archival high-dispersion ultraviolet spectra obtained by the International Ultraviolet Explorer reveal sharp shortward-shifted features in the spectra of O subdwarfs. In three examples presented here, BD + 75.325 deg, HD 128220 B, and BD + 28.4211 deg, stable, multiple, discrete shortward-shifted components of the N V, C IV, and Si IV resonance doublets are seen. The available data suggest that some of these features are persistent, being relatively stable in velocity and intensity over at least 9 months. It is tentatively suggested that the mechanism, or mechanisms, producing these discrete features operates universally in hot stars, from luminous O and B stars down through the O subdwarfs to include the hot white dwarfs. If true, this has important ramifications for current knowledge of mass loss in hot stars.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 274; L87-L91
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 31
    facet.materialart.
    Unknown
    Images in the rocket ultraviolet - The starburst in the nucleus of M83 (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Ultraviolet images of the SAB(s)c I-II galaxy M83 (NGC 5236) obtained with a rocketborne telescope in broad bandpasses centered at 1540 A and 2360 A show a bright resolved nuclear source which accounts for approximately 20 percent of the flux of the galaxy in both bandpasses. Low-resolution International Ultraviolet Explorer spectra of this source reveal an energy distribution similar to that of the starburst nucleus of NGC 7714. Strong blueshifted absorption lines can be interpreted as evidence for a nuclear wind powered by supernovae. Observations from UV, X-ray, optical, and far-infrared bandpasses are consistent with a starburst approximately one-sixth as strong as that in M82. A scaling of the M82 models of Rieke et al. (1980) predicts that the nucleus of M83 contains 10 to the 6th - 3 x 10 to the 7th solar masses in young stars and has a supernova rate of approximately 0.01 per yr.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 274; L53-L56
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 32
    facet.materialart.
    Unknown
    X-ray observations of LMC X-3 with the monitor proportional counter aboard the HEAO 2 Einstein observatory - A comparison with Cygnus X-1 (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: A comparison is presented of the black hole candidates LMC X-3 and Cygnus X-1 based on Einstein observations of LMC X-3 with the monitor proportional counter. A spectral analysis shows LMC X-3 to be more like the typical bright galactic X-ray source than Cygnus X-1. A search for periodic pulsations over a period range from 0.2 ms to over 1000 s set upper limits at the 90 percent confidence level of the order of 10 percent. An analysis of the aperiodic variability of LMC X-3 shows none of the shot noise behavior characteristic of Cygnus X-1. The absence of distinctive X-ray properties common to both sources suggests that the identification of black hole candidates on the basis of X-ray properties similar to Cygnus X-1 (or LMC X-3) is not reliable.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 274; L65-L69
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 33
    facet.materialart.
    Unknown
    Stellar evolution in N-body simulations of disk galaxies. I (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The Kalnajs (1972, 1976) Omega models of global mass and velocity distributions are employed in the present two-dimensional N-body simulation, which allows for a spectrum of particle masses, stellar explosions, explosion remnant interactions with an interstellar medium, and the creation of new stars from the gas. Two sequences of runs using the Omega values of 0.8 and 0.9 examine the separate and combined effects of particle mass distribution, the gravitational influence of an interstellar gas distribution on the N-body particles, and stellar evolution, allowing for stellar explosions and star formation from the gas. It is found that both Omega values' nonequilibrium results dramatically change when evolution is allowed to occur. These results call for more realistic coupled N-body and evolution simulations in order to improve the understanding of disk galaxy evolution.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 274; 595-610
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 34
    facet.materialart.
    Unknown
    The (an)isotropy of the X-ray sky (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: An assessment is made of the extent to which the study of the isotropy of the X-ray sky has contributed to the present understanding of the structure of the universe at moderate redshifts. It is, of course, the anisotropic character of the sky flux that is valuable in this context. Although it is not currently possible to undertake measurements with the precision and small solid angles that are typically achieved in the microwave range, the comparatively crude limits from the X-ray fluctuations place limits on the largest scale structure of the universe. After indicating the nature of measurements made, with the HEAO 1 A-2 experiment, of the X-ray sky and its anisotropies, it is shown how these place limits on the origin of the X-ray sky and on any large scale structure of the universe.
    Keywords: ASTROPHYSICS
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 35
    facet.materialart.
    Unknown
    Accuracy of approximations to the Navier-Stokes equations (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The systems of truncated differential equations that have been proposed to reduce the complexity and large computational costs of solutions to the full Navier-Stokes equations are considered. These systems are computationally efficient and capture all the physically relevant behavior. The systems follow a certain hierarchy: (1) the classical boundary-layer equations with specified edge properties (usually the streamwise pressure distribution); (2) the coupled boundary-layer/inviscid equations; (3) the so-called thin-layer equations that discard streamwise diffusion; and (4) the Navier-Stokes equations. Consideration is given to each of these approximations applied to an incompressible, laminar-separating flow at low and moderate Reynolds numbers. It is pointed out that for any flow or region of flow for which viscous-inviscid interaction effects are small, classical boundary-layer equations will provide a satisfactory description of the viscous flow at a fraction of the computational cost of any higher approximations.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA Journal (ISSN 0001-1452); 21; 1759
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 36
    facet.materialart.
    Unknown
    Comments concerning magnetic fields as a possible cause of rapid, irregular variability of early-type stars (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: It is noted that it is helpful to divide the atmosphere of an early-type star into two parts: a photosphere and a mantle. The photosphere can be modeled satisfactorily by normal model-atmosphere procedures. When modeling the mantle, one must take account of the deposition of nonradiative heat and momentum and one should recognize that the mantles of hot stars do not appear to be uniform or spherically symmetric. Five areas of discrepancy between classical theory and observation are noted and a possible way of modeling the mantles of early-type stars is outlined. The model consists of arcades of magnetic loops which form helmet-type structures in the equatorial band of the star, and of coronal-hole-type structures emmanating from weak unipolar regions which are chiefly distributed at polar latitudes.
    Keywords: ASTROPHYSICS
    Type: Hvar Observatory, Bulletin (ISSN 0351-2651); 7; 1, 19
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 37
    facet.materialart.
    Unknown
    Observational knowledge about the physical properties of O stars (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Information about the effective temperatures, radii, and masses of O-type stars is presented. It is argued that rapid variations in the amount of light from O stars and the spectral distribution are a result chiefly of changes which occur in the envelope of the star. The stability of the photospheric layers of O stars against convection is reviewed and it is noted that late O stars and early B stars have a convection zone in the deeper parts of the photosphere. This convection zone is due to the second ionization of helium. Evidence is reviewed that most of the line-profile changes seen for O stars are generated by changes in the physical state of the mantle of the star, that is of the outer atmosphere where the deposition of non-radiative energy and momentum controls the physical state of the atmosphere. The physical state of the mantle may change in response to changes in the upper envelope of a star with a different time constant than the photosphere does.
    Keywords: ASTROPHYSICS
    Type: Hvar Observatory, Bulletin (ISSN 0351-2651); 7; 1, 19; 1-15; Di
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 38
    facet.materialart.
    Unknown
    Growth of Goertler vortices in compressible boundary layers along curved surfaces (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: An investigation of the growth of the three-dimensional, counter-rotating, longitudinal type vortices is considered in two-dimensional laminar compressible boundary-layer flow. The basic approximation of the disturbance equations that includes the terms due to boundary layer growth is considered and solved numerically. These terms are shown to have large local effects near the neutral stability region. The study shows that the instability of the boundary layer with respect to the three-dimensional vortices sets in at higher Goertler number as Mach number increases. Also the maximum amplitude ratio of the vortices is reduced by about 20 percent as Mach number increases from 0 to 5.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Engineering and Applied Sciences (ISSN 0191-9539); 2; 3, 19; 213-238
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 39
    facet.materialart.
    Unknown
    Numerical models for cometary dust environments (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The development of a numerical model for the dust environment near a comet is described. The major components of the model are a simple treatment of the acceleration of the dust by the gas outflow from an isothermal icy nucleus, a detailed treatment of the dust particle trajectories controlled by solar gravity and radiation pressure, including the formation of the dust envelope and tail, and a simple treatment of the radiation from the dust in the visible and thermal infrared. The results of recent comet observations are used to estimate parameter values for the model, including dust-to-gas ratios by light and by mass, the distribution of dust and gas emission on the nuclear surface, the distributions of dust particle size, density, mass, and radiative properties, and other quantities. Gas and dust production rates as functions of time are derived from observed light curves using the simple photometric theory. Sample results are presented for the dust concentration, flux and fluence along the trajectory of a spacecraft which flies by Comet P/Halley in 1986.
    Keywords: ASTROPHYSICS
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 40
    facet.materialart.
    Unknown
    An outer ion coma model in two dimension (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: A simple cometary outer ion coma model is constructed by adopting published results from numerical MHD computations. The ion composition and density distributions so derived are used to highlight some of the basic features of cometary plasma flows and the need for cometary ion observations with absolute brightness calibration.
    Keywords: ASTROPHYSICS
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 41
    facet.materialart.
    Unknown
    Search for hydrogen atoms and the noble gas abundances in the head of Comet Schwassmann - Wachmann 1 (1974 II) from Voyager 2 UVS spectra (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Keywords: ASTROPHYSICS
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 42
    facet.materialart.
    Unknown
    The nature of cometary dust from remote sensing (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Observational data on the thermal emission from cometary dust grains and theoretical models constructed to explain them are reviewed. Consideration is given to grain temperature, the size distribution of the grains, thermal-emission models, the silicate component, dust-grain albedo, and icy grains; model predictions and observations are compared in graphs. It is pointed out that no unambiguous detection of icy grains has been achieved, probably because these grains are vaporized within a few hundred km of the nucleus when the comet is within 2.5 AU of the sun.
    Keywords: ASTROPHYSICS
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 43
    facet.materialart.
    Unknown
    Finite element calculation of buoyancy-driven convection near a melt/solid phase boundary (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Two iterative schemes based on the mixed finite element method are developed for analyzing steady natural convection in a melt adjacent to its solid phase. The simplest method decouples the calculation of the field variables and the shape of the melt/solid interface into two interlocked iterations that are performed successively. The second method uses Newton's iteration to solve simultaneously for both types of unknowns and has a quadratic convergence rate. Results for a model problem of melt and solid in a cylindrical ampoule show the Newton algorithm to be a factor of three more efficient.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 44
    facet.materialart.
    Unknown
    Electromagnetically-tracked free-mass gravitational wave antennas (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The response to a gravitational wave of two free masses whose relative motion is monitored with an electromagnetic tracking signal is derived. The results indicate a two-feature signature in one-way data and a three-feature signature in two-way data. The effect is applied to gravitational wave experiments using laser interferometers, spacecraft Doppler tracking, planetary ranging, and pulsar timing analysis. Actual results are presented from spacecraft Doppler experiments and from pulsar timing data analysis, with new upper limits being set on a possible cosmic gravitational wave background via the pulsar data.
    Keywords: ASTROPHYSICS
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 45
    facet.materialart.
    Unknown
    Infrared properties of extragalactic H II complexes (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Infrared observations of relatively isolated giant H II complexes in the LMC and the spiral arms of M33 and M101 are discussed, and complexes which extend over several kiloparsecs near the galactic centers are examined. The 30 Doradus nebula is emphasized, showing the variation of the 50-100 micron color temperature with position in that object. Ten-micron scans through the nucleus of NGC 1097 are compared to a visual photograph, showing the enhanced infrared emission which occurs at the nucleus and at the ring of H II regions about 1 kpc from the nucleus.
    Keywords: ASTROPHYSICS
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 46
    facet.materialart.
    Unknown
    Multiple-grid convergence acceleration of viscous and inviscid flow computations (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: A multiple-grid algorithm for use in efficiently obtaining steady solution to the Euler and Navier-Stokes equations is presented. The convergence of a simple, explicit fine-grid solution procedure is accelerated on a sequence of successively coarser grids by a coarse-grid information propagation method which rapidly eliminates transients from the computational domain. This use of multiple-gridding to increase the convergence rate results is substantially reduced work requirements for the numerical solution of a wide range of flow problems. Computational results are presented for subsonic and transonic inviscid flows and for laminar and turbulent, attached and separated, subsonic viscous flows. Work reduction factors as large as eight, in comparison to the basic fine-grid algorithm, were obtained. Possibilities for further performance improvement are discussed. Previously announced in STAR as N83-21847
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Applied Mathematics and Computation (ISSN 0096-3003); 13; 375-398
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 47
    facet.materialart.
    Unknown
    X-ray emission from pre-main-sequence stars, molecular clouds and star formation (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The pre-main sequence X-ray emitting stars observed in molecular clouds appear to provide the bulk of the ionization. Newly forming stars therefore control the coupling of the magnetic field to the cloud. Since this coupling itself is believed to be responsible for the rate of cloud collapse, it is suggested that there is a natural feedback mechanism, involving observed X-rays, which is capable of regulating molecular cloud evolution and the rate of star formation.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 272; Sept. 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 48
    facet.materialart.
    Unknown
    A note on compressibility and energy cascade in turbulent molecular clouds (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Observed velocity-size correlations are reexamined in the light of an improved theory of turbulent energy cascade that is developed. It is shown that observed velocity-size correlations cannot be compared with the Kolmogorov law, which is based on incompressible turbulent flow. The fact that the log v-log(l/rho) scaling law (v the turbulent velocity, l the associated region size, and rho the fluid density) predicted for compressible energy cascade is always steeper than that observed in molecular clouds indicates the injection rather than the dissipation of mechanical energy at smaller scales of motion. It is also shown that the concept of strict energy cascade may not be generally applicable in the interstellar medium. The agreement between theory and observation turns out to be best for small cool clouds and cloud cores, suggesting that, for these regions at least, the dominant process in establishing the observed v-l-rho correlation is a turbulent energy cascade.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 272; Sept. 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 49
    facet.materialart.
    Unknown
    A large molecular cloud toward the SNR W50 and SS 433 (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The CO 1 yields 0 transition at 115 GHz has been mapped over an area of more than 6 deg sq toward W50, the extended SNR surrounding the peculiar object SS 433. W50 is found to lie at the end of a filamentary molecular cloud 4 deg long and 1 deg wide that closely matches a conspicuous dust lane on the Palomar Sky Survey; the cloud's kinematic distance is within 0.7 of 2.2 kpc, in agreement with the distance 2-3.3 kpc estimated for the SNR, and its mass is about 120,000 solar masses. Though there is little evidence of star formation in the molecular filament, or evidence of an interaction between the filament and W50 (or SS 433), the positional coincidence of the two, their similar distance, and their displacement nearly two molecular scale heights from the plane all suggest a physical relationship or common origin. One possibility is that both the molecular filament and the stellar progenitor of W50 were ejected from a large active molecular complex lying in the plane at l = 40 deg.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 272; Sept. 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 50
    facet.materialart.
    Unknown
    Correlated particle and magnetic field observations of a large-scale magnetic loop structure behind an interplanetary shock (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: From a survey of observations on ISEE-3, an example of correlated particle and magnetic field observations of a large-scale magnetic loop structure is presented. Bidirectional proton fluxes were observed for a period of 40 hours in the energy range 35-1600 keV approximately 12 hours after the passage of the interplanetary shock of December 11, 1980, and directly after the passage of a discontinuity. For each of the eight logarithmically spaced energy channels, a three-dimensional anisotropy analysis reveals streaming along both directions of the magnetic field. The magnetic field rotated slowly but steadily through approximately 180 deg during this same 40-hour period; this is consistent with the existence of a large-scale loop with extent greater than 0.5 AU. The observations suggest that the particles are being injected into the loop sunward of the spacecraft; they appear as bidirectional fluxes in the outermost regions of the loop arising from a combination of focusing and near scatter-free transport.
    Keywords: ASTROPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 10; Sept
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 51
    facet.materialart.
    Unknown
    Effect of variable thermal conductivity on isotherms in Bridgman growth (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: A change in thermal conductivity associated with melting or solidification can have a profound influence on the isotherms near the solidification interface if the material is being directionally solidified in an ampoule whose walls carry a substantial portion of the heat. This analysis was prompted by a recent discovery that the thermal conductivity of Hg(1-x)CD(x)Te increased dramatically as the material is heated above the solidus curve. An illustrative example is shown in which the sample is approximated as an infinite cylinder with constant but diffferent thermal properties in the solid and melt. The boundary conditions are fixed on the surface by a conductive ampoule in a two-zone Bridgman furnace with an adiabatic region separating the two zones. The effect of the adiabatic zone in this case is to intensify the curvature of the interface rather than to lessen it.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Crystal Growth (ISSN 0022-0248); 61; Apr
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 52
    facet.materialart.
    Unknown
    The effect of MHD instabilities on the flaring of cometary plasma tails (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The hypersonic pressure balance model of flaring in cometary plasma tails of Ershkovich et al. (1982) has been modified to include the effects of magnetohydrodynamic (MHD) instabilities occurring along the ionopause in the outer-tail regions. The effect of instability is to mix the solar-wind and comet-tail plasmas, increasing the tail magnetic field strength above that calculated from magnetic flux conservation. The earlier model assumed the ionopause to be a tangential discontinuity surface (flux conserving) at all distances, with the result that the magnetic field approached zero in the outer regions of strongly flaring tails. The present model is more realistic and is in better agreement with measurements of cometary plasma tail widths and flaring angles. This agreement leads to an important conclusion that the magnetic flux is not conserved in distant comet tails.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 272; Sept. 1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 53
    facet.materialart.
    Unknown
    On searches for periodic pulsed emission - The Rayleigh test compared to epoch folding (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The Rayleigh test has been recently invoked as a method of searching a time series for periodic pulsations. In this paper, this technique is discussed and compared to epoch folding, a technique which has had widespread use in X-ray astronomy. It is found that the Rayleigh test provides a more sensitive approach to the search for periodic pulsations when the pulses are sinusoidal or of broad duty cycle, such as those typical of the pulsing X-ray sources. Epoch folding, on the other hand, is more sensitive to the narrow pulses typical of radio pulsars.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 272; Sept. 1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 54
    facet.materialart.
    Unknown
    Electrodynamic coupling in magnetically confined X-ray plasmas of astrophysical origin (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Explicitly magnetic field-independent relationships that quantitatively connect the thermodynamic state of the confined beta-less-than-one X-ray plasma to the confining magnetic loop characteristics and the stressing velocity at beta greater than about one are presented. The derived relations fall into two categories: (1) diffuse heating resulting from efficient transport of energy throughout the magnetic loop volume, and (2) isolated heating within the electrodynamic dissipation shell. For each of these cases the Joule dissipation, shear viscous dissipation, and compressional dissipation are considered. Each of these models is characterized by three thermodynamic scalings that are parametrized by the magnetic loop properties and by the stressing velocity. Eliminating the magnetic field intermediary from these relations and normalizing the inverse aspect ratio and the magnetic expansion factor with respect to solar conditions results in a single, unique velocity scaling law for each model.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 271; Aug. 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 55
    facet.materialart.
    Unknown
    Analysis of coolant entrance boundary shape of porous region to control cooling along exit boundary (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: A cooled porous region has a plane surface exposed to a specified spatially varying heat flux. The coolant leaves the region through this surface, and it is desired to control the flow distribution to maintain a specified uniform surface temperature. This is accomplished by having the coolant entrance surface shaped to provide in the region the necessary variation of path length and, hence, flow resistance. The surface shape at the coolant entrance is found by solving a Cauchy boundary value problem. An exact solution is obtained that will deal with a wide variety of heating distributions for both two- and three-dimensional shapes.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: ASME, Transactions, Journal of Heat Transfer (ISSN 0022-1481); 105; Aug. 198
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 56
    facet.materialart.
    Unknown
    The detection of H2 in cool carbon stars (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Spectra of several carbon stars in the two micron region are examined and compared with synthetic spectra from model atmospheres. Molecular hydrogen has been directly observed in carbon stars for the first time through the quadrupole 1-0 S(1) line at 4712.9/cm. It is definitely present in several Mira variables, and is definitely not present in several irregular variables and one Mira variable. A discrepancy between the predicted and observed line depths at different temperatures is shown. Resolution of the discrepancy by change of temperature alone would require an upward revision of the present effective temperature scale by at least 600 K. Several possible resolutions of the dilemma are briefly examined.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 270; July 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 57
    facet.materialart.
    Unknown
    Very long baseline interferometry at a wavelength of 3.4 mm (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The first detection of interference fringes by VLBI at a wavelength of 3.4 mm during observations of 3C84 are reported. The compact source in the nucleus of 3C84 was observed for a 9-hr period on the 485 km baseline between the Owens Valley Radio Observatory and the Hat Creek Observatory. The fringe data are given and the derivation of the correlated flux densities is described. The findings are discused in the context of previous obervations. The results demonstrate that there are no unforeseen technical difficulties associated with millimeter VLBI, and that the sensitivity of existing systems is sufficient to observe objects brighter than a few Jy. The observations are consistent with the millimeter wavelength radio structure of 3C84 being more compact than its centimeter wavelength structure.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 303; June 9
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 58
    facet.materialart.
    Unknown
    Comment on 'A comparative study of rotational properties of high-velocity and low-velocity early-type stars' (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 267
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 59
    facet.materialart.
    Unknown
    Theoretical study of silicon dicarbide (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Silicon dicarbide was first observed in 1926 in spectra of cool carbon stars. The carrier of these bands around 5000 A was tentatively identified as SiC2 by Kleman (1956) who produced similar spectra by inserting silicon into the graphite tube of a King furnace heated to over 2500 K. This identification was strengthened by subsequent mass spectral studies which showed SiC2 as a major molecular component of vaporized silicon carbide. The present investigation is concerned with calculations which were initiated in an attempt to understand more recent astronomical observations of unidentified lines in the millimeter-wave region of the spectrum. The calculations were designed to determine the ground state equilibrium structure and to obtain vibrational and rotational constants. Calculations for estimating the positions and structure of low-lying electronic states were also performed. Self-consistent field (SCF) calculations were performed assuming a closed-shell electronic structure analogous to that in C3. Calculations were conducted for symmetric CSiC, and asymmetric SiCC forms.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 266
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 60
    facet.materialart.
    Unknown
    A two-component X-ray spectrum from SMC X-1 (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: HEAO 1 A-2 and Einstein Solid State Spectrometer (SSS) observations of SMC X-1 are presented. An unpulsed soft component is found with a blackbody temperature of 0.16 keV and an area for the emission region of 10 to the 15th to 10 to the 17th sq cm. The hard X-ray component is pulsed; the phase-averaged spectrum is a power law with alpha of about 0.5 up to 17 keV, above which it steepens. The SSS sets an upper limit of less than 4 x 10 to the 21st H/sq cm to any absorption, and is consistent with that expected from the wind of Sk 160. Absorption dips with a timescale of several hundred seconds are seen immediately following an eclipse exit, and are probably caused by inhomogeneities in the wind of Sk 160.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 266
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 61
    facet.materialart.
    Unknown
    NGC 315 - High-velocity H I in an active elliptical galaxy (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The detection of high-velocity H I in absorption against the nuclear continuum source in the giant elliptical galaxy NGC 315 is reported. The absorption line is found to be highly blueshifted in the reference frame of the galaxy with a projected velocity toward the galaxy of 490 km/s. The absorption line is very strong (244 + or - 4 mJy), consisting of two components with very narrow velocity widths of 2.5 km/s (FWHM) each and peak optical depths of 0.9 and 0.2. The kinetic temperature must be 150 K if the line widths are due entirely to thermal broadening, while the neutral gas column densities implied are 2-5 x 10 to the 20th hydrogen atoms/sq cm. No OH in absorption was detected in these clouds to a limiting peak optical depth of 0.04, although this result is consistent with either a galactic or extragalactic origin of the clouds. It is suggested that these clouds may have condensed out of a large unobserved galactic halo of gas, or they may reside in or have been captured from the intracluster medium.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 266
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 62
    facet.materialart.
    Unknown
    The angular diameters, effective temperatures, radii, and luminosities of 10 Wolf-Rayet stars (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The effective temperature of a normal star with an absorption-line spectrum is a parameter which represents the total amount of radiative energy emerging from each square centimeter of surface of the star. Effective temperatures have been obtained for 10 Wolf-Rayet stars by means of ultraviolet energies determined from high-resolution International Ultraviolet Explorer (IUE) spectra and energies determined from observations made in the visible range. It is essential to use high-resolution IUE spectra in order to resolve the continuum from many emission lines which are present, particularly shortward of 1900 A. The results confirm what was found earlier, namely that the effective temperatures of Wolf-Rayet stars are similar to those of early B stars. The effective temperature of the central star of the planetary nebula BD 30 deg 3639, HD 184738, is found to be 18,000 K.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 266
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 63
    facet.materialart.
    Unknown
    Axions and the evolution of structure in the universe (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: A cosmological scenario where axions provide the dark matter in the universe is considered. Fluctuations in the axion-field energy denisty produced by domain walls and strings cause the appearance of 'axion clumps' of masses of order 10 to the 6th solar masses which most likely collapse to black holes by or at the time that the universe becomes axion dominated at T approximately 10 eV. These objects form the building blocks for the clustering hierarchy theory of galaxy and supercluster formation on scales up to about 10 Mpc and 10 to the 15th solar masses.
    Keywords: ASTROPHYSICS
    Type: Physical Review Letters; 50; Mar. 21
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 64
    facet.materialart.
    Unknown
    On searches for pulsed emission with application to four globular cluster X-ray sources - NGC 1851, 6441, 6624, and 6712 (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Periodic pulsations have been sought in the NGC 1851, 6441, 6624, and 6712 globular cluster sources' X-ray emission, using the Einstein Observatory's Monitor Proportional Counter. Special attention is given to features of the present methods of analysis, which correctly account for several effects that have been routinely overlooked by other researchers. No pulsed emission was detected in the periods searched, which covered from 1 msec to about 500 sec. The 90% confidence upper limits for the pulsed fraction are given.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 266
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 65
    facet.materialart.
    Unknown
    Numerical solutions for spin-up from rest in a cylinder (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: A set of three-dimensional flow-field data for the region around a cylinder impulsively spun-up from rest was derived with a numerical model based on the Navier-Stokes equations. Laser-Doppler anemometer data in the azimuthal direction was employed to test the model predictions, and data was developed for a flowfield with Ekman numbers from 9.18/1,000,000 to 9.18/10,000. The contributions of inviscid and viscous terms were determined as functions of radius and time. It was found that immediately after start-up viscous diffusion is the dominant factor, which is replaced by nonlinear radial advection. The Coriolis force dominates in the later stages of spin-up. The inward radial flow is a maximum near the front, where the vertical velocity is small, but features strong radial gradients, as it does at the edge of the Ekman layer.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Fluid Mechanics; 127; Feb. 198
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 66
    facet.materialart.
    Unknown
    Possible mechanisms for the Hubble-Sandage /S Doradus/ variables (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The unexplained long-term variability of the light of the brightest nonexplosive stars known, namely the Hubble-Sandage (or S Doradus) variables, is investigated in terms of the following mechanisms: (1) episodic, nearly catastrophic mass loss, perhaps accompanied by temporary shrinkage of the stellar radius, in a luminous supergiant; (2) flickering of a hydrogen-burning or helium-burning shell; (3) hydrogen flashing in an evolved stellar core; (4) pulsation of a luminous supergiant envelope near the Eddington limit of radiative stability; (5) pulsation of a dense circumstellar gas or dust cloud; (6) overturning of giant convection cells (or some other kind or nonradial oscillation) in a luminous supergiant envelope; or (7) vibrational instability and mass outflow in an extremely massive main-sequence star. It is believed that the second and third suggestions can all but definitely be ruled out and that the sixth and seventh are rather unlikely. Preference is given to the notion that a sudden, massive outflow of matter may sometimes occur from the surface of an evolved supergiant of very high mass.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 264
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 67
    facet.materialart.
    Unknown
    Methanol in Orion A - Simultaneous observations of corresponding rotational transitions in the ground and torsionally excited states (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 264
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 68
    facet.materialart.
    Unknown
    Hf chronometer for the early solar system (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: It is now widely believed that Al-26 (half-life, 7.2 x 10 to the 5th yr) and Pd-107 (half-life, 6.5 x 10 to the 6th yr) were present in the early solar system. The nucleosynthetic event responsible for the production of these nuclei must therefore have occurred no more than a few million years before the formation of solid bodies. It is possible that this event also gave a rise to the I-129 believed to be present in the early solar system. The last event to contribute Pu-244 to the solar system, however, occurred approximately 10 to the 8th yr before the time of solidification. It is noted that this latter time scale is also consistent with the lack of evidence for a Cm-247 chronometer. It is proposed that Hf-182 (half-life, 9 x 10 to the 6th yr) can resolve the question whether heavy-element nonactinide nucleosynthesis occurred during the (Al-26)-producing event. It is believed that an answer to this question will help to clarify the chronology of the formation of the solar system and will help to determine the astrophysical sites of heavy-element nucleosynthesis.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 304; Aug. 11
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 69
    facet.materialart.
    Unknown
    Accretion powered X-ray pulsars (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The current theoretical understanding of the properties of X-ray pulsars is assessed through a comparison with unified descriptions of 14 such systems, extending over six orders of magnitude in luminosity, in whose phase averaged spectra the only notable trend is a less abrupt high energy cutoff in the lower luminosity systems. Detailed pulse phase spectroscopy is given for five of the systems. A reexamination of the pulse phase spectra of 4U 0115 + 63 has uncovered electron cyclotron lines at 11.5 and 23 keV that appear to be in absorption at pulse peak and in emission during an interpulse. Spectral hardening regions such as those from Her X-1 are a common feature in the low energy pulse of many pulsars, and may represent the passage of the magnetic axis through the observer's line of sight. Attention is given to the nature of the beaming from Her X-1, and it is concluded that a pencil beam configuration represents the simplest explanation of the overall properties of the pulse.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 270; July 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 70
    facet.materialart.
    Unknown
    Scalloped disk galaxies - A Kelvin-Helmholtz instability? (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The scalloped outermost edge of the Galaxy may be driven by a Kelvin-Helmholtz interface instability if the disk and halo components of the Galaxy at large galactocentric distances do not corotate. The range of unstable wavelengths is found to be 10-23 kpc, in good agreement with the observed wavelength, 19 kpc.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 270; July 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 71
    facet.materialart.
    Unknown
    Fragmentation of a nonisothermal protostellar cloud (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The collapse of a very low thermal energy, rotating cloud results in fragmentation to a binary protostellar system even in the nonisothermal regime. The solar system therefore probably did not form from a fragmentation hierarchy involving ejection of the presolar nebula from a multiple system.
    Keywords: ASTROPHYSICS
    Type: Icarus (ISSN 0019-1035); 55; July 198
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 72
    facet.materialart.
    Unknown
    Procedure for generating ground wind environments for Shuttle liftoff studies (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Ground-wind environments for Monte Carlo simulations of Space Shuttle liftoff at KSC are developed. Input parameters include randomly selected 18.3-m-altitude peak wind speed (from which mean wind profile and turbulence intensity are calculated), randomly selected mean wind direction, and longitudinal and lateral turbulence components obtained from the Shuttle-simulation turbulence tapes (SSTT: Tatom et al., 1982). The steps in the simulation of turbulence time histories and horizontal wind fields are listed. It is found that separate statistical analysis of each hour-season pair, applying data on the time fraction of occurrence of peak winds and wind directions at KSC, will be necessary to interpret simulation results consistently.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Spacecraft and Rockets (ISSN 0022-4560); 20; July-Aug
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 73
    facet.materialart.
    Unknown
    The partial phase of the eclipse of epsilon Aurigae (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Ultraviolet spectra of the peculiar eclipsing binary Epsilon Aurigae (FO Ia + ?) were obtained with the International Ultraviolet Explorer at pre-eclipse and ingress partial phases. The results show a wavelength dependence of the eclipse in contrast to the grayness (non-wavelength dependence) of the eclipse observed in visible light. From the current results, incorporating previous observations, it is suggested that: (1) the obscuration of the light of the F supergiant by the disk proposed by Huang (1965) is the result of electron scattering in visible light; (2) the increase in the eclipse depths toward shorter wavelengths observed in the ultraviolet is caused by dust; and (3) the temperature of the disk is in the range from 1000 to 2000 K.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 269; June 1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 74
    facet.materialart.
    Unknown
    Effects of the Kelvin-Helmholtz surface instability on supersonic jets (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: An exact numerical calculation is provided for of linear growth and phase velocity of Kelvin-Helmholtz unstable wave modes on a supersonic jet of cylindrical cross section. An expression for the maximally unstable wavenumber of each wave mode is found. Provided a sharp velocity discontinuity exists all wave modes are unstable. A combination of rapid jet expansion and velocity shear across a jet can effectively stabilize all wave modes. The more likely case of slow jet expansion and of velocity shear at the jet surface allows wave modes with maximally unstable wavelength longer than or on the order of the jet radius to grow. The relative energy in different wave modes and effect on the jet is investigated. Energy input into a jet resulting from surface instability is discussed. Previously announced in STAR as N83-17379
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 269; June 1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 75
    facet.materialart.
    Unknown
    Observations of the line profile of Paschen alpha in 3C 273 (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Within the uncertainties, the P-alpha line profile is the same as those of H-beta, L-alpha, and C IV. It is therefore contended that if current models of broad-line-emitting clouds in quasars are correct, then the similarity of the P-alpha line profile to the L-alpha profile argues against a velocity field dominated by radial inflow or outflow. It is noted, however, that if the cloud motions are predominantly due to radial inflow or outflow, then the clouds must radiate more isotropically in L-alpha then current models predict. The observed similarity of the line profiles of P-alpha at 1.875 microns and of C IV at 1550 A leads to the conclusion that there is no differential reddening caused by dust between clouds moving at different velocities within the broad line region of 3C 273.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 95; May 1983
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 76
    facet.materialart.
    Unknown
    Energy dynamics in stressed magnetic fields - The filamentation and flare instabilities (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The thermal and tearing instabilities are believed to be the two primary temperature modification mechanisms in sheared astrophysical magnetic fields. The former gives rise to the formation of cool filaments and the latter to the release of magnetic energy. It has long been known that these processes are interrelated, most conspicuously in the case of the solar corona where prominences often precede flares within the same magnetic structure. It is also clear, from first principles, that the energy transport underlying the thermal instability should have a strong effect on the resistivity which facilitates magnetic tearing, and that the energy release of the latter should affect the temperature drop of the former. This paper describes some results of the first calculations which attempt to unify the dynamic treatment of these two coexisting instabilities. Growth rates as a function of resistivity, and examples of the primary mode structures are provided, along with a discussion of some critical aspects of the interaction of these two astrophysical energy flux mechanisms.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 268; May 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 77
    facet.materialart.
    Unknown
    Blue compact dwarf galaxies. II - Near-infrared studies and stellar populations (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: An IR photometric survey was performed of 36 blue compact dwarf galaxies (BCDG) where intense bursts of star formation have been observed. The survey covered the J, H, and K lines, with all readings taken at the level of a few mJy. Although the near-IR fluxes observed in the galaxies are due to K and M giants, the bursts have calculated ages of less than 50 million yr. However, the BCDG galaxies surveyed are not young, with the least chemically evolved galaxy observed, I Zw 18, featuring 50 pct of its stars formed prior to its last burst, but with a missing mass that is not accounted for by H I interferometric observations. It is concluded that the old stars must be more spatially extended than the young stars, and a mixture of OB stars with the K and M giants is projected as capable of displaying the colors observed. The star formation processes in the BCDG galaxies is defined as dependent on the total mass of the galaxies, with low mass galaxies having a high ratio of star formation, compared to their previous rates.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 268; May 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 78
    facet.materialart.
    Unknown
    Observation of ice mantles toward HD 29647 (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The water ice absorption band at 3.1 microns has been observed in HD 29647, which is a late B type star with an anomalous ultraviolet extinction curve. The interpretation is that ice mantles are present on the dust grains in the intervening cloud and that these mantles are responsible for suppressing the 2200 A interstellar absorption feature. This is the first observation of both the 2200 A region and the 3.1 micron interstellar absorption feature toward the same star. A comparison of recent UV laboratory data of water ice with the UV spectrum of HD 29647 further supports the presence of water ice mantles in the same column density as that observed in the infrared. The diffuse interstellar features have been reported to be weakened in this star, consistent with their origin being on grain core surfaces, rather than in mantles or gaseous molecules.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 268; May 1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 79
    facet.materialart.
    Unknown
    The kinetic temperature and density of the Sagittarius B2 molecular cloud from observations of methyl cyanide (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Observations of the K components of the CH3CN J = 4-to-3 rotational transition at 73.6 GHz, the 6-to-5 transition at 110.4 GHz, and the 7-to-6 transition at 128.7 GHz, yield a mean kinetic temperature value of 85 + or - 10 K and a mean H2 density of 110,000 + or - 50,000/cu cm for the central 2.0 arcmin of the Sgr B2 molecular cloud. Within the K = zero-to-4 ladders of CH3CN in Sgr B2, the populations of the radiatively coupled J levels are relaxed and exhibit a rotational temperature of about 16 K, which is similar to that of several linear molecules.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 266
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 80
    facet.materialart.
    Unknown
    The evolution of Tollmien-Schlichting waves near a leading edge (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The method of matched asymptotic expansions is used to study the generation of Tollmien-Schlichting waves by free-stream disturbances incident on a flat-plate boundary layer. Near the leading edge, the motion is governed by the unsteady boundary-layer equation, while farther downstream it is governed (to lowest order) by the Orr-Sommerfeld equation with slowly varying coefficients. It is shown that there is an overlap domain where the Tollmien-Schlichting wave solutions to the Orr-Sommerfeld equation and appropriate asymptotic solutions of the unsteady boundary-layer equation match, in the matched-asymptotic-expansion sense. The analysis explains how long-wavelength free-stream disturbances can generate Tollmien-Schlichting waves of much shorter wavelength. It also leads to a set of scaling laws for the asymptotic structure of the unsteady boundary layer.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Fluid Mechanics; 127; Feb. 198
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 81
    facet.materialart.
    Unknown
    Sparger system for MMH-helium vents (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Based on a calculated vent flow rate and MMH concentration, a TI-59 program was run to determine total sparger hole area for a given sparger inlet pressure. Hole diameter is determined from a mass transfer analysis in the holding tank to achieve complete capture of MMH. In addition, based on oxidation kinetics and vapor pressure data, MMh atmospheric concentrations are determined 2 ft above the holding tank.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: The 1983 NASA(ASEE Summer Faculty Fellowship Research Program Research Reports; 17 p
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 82
    facet.materialart.
    Unknown
    Development of a mass spectrometer system for the measurement of inert gases in meteorites (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The study of the inert gases in meteorites has provided many clues as to the origin and evolution of the solar system. Particularly crucial and complex are the gases krypton and xenon. To accurately measure the isotopic compositions of these gases requires a mass spectrometer of high sensitivity and resolution. A previously unused and largely untested mass spectrometer system was brought to the point where it was ready for routine sample analyses. This involved, among other things, focusing the ion beam for optimal peak shape and sensitivity, documenting the instrument's response to a series of characteristic tests such as multplier gain checks, and interfacing the instrument to a computer to run the sample analyses. Following this testing and setting up, three iron meteorite samples were to be analyzed for argon, krypton, and xenon. The three samples were shown in prior work to possibly contain primordial heavy inert gases. Although these analyses have not yet been carried out, it is anticipated that they will be completed in the near future.
    Keywords: ASTROPHYSICS
    Type: NASA. Johnson (Lyndon B.) Space Center The 1983 NASA/ASEE Summer Faculty Fellowship Research Program Research Reports; NASA. Johnson (Lynd
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 83
    facet.materialart.
    Unknown
    An analysis of cryotrap heat exchanger performance test data (400 area) and recommendations for a system to handle Apollo RCS engines (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The current arrangement of a Platecoil heat exchanger which uses LN2 on the inside of parallel tubes, in counter flow to the test cell engine exhaust gases which are drawn through a box surrounding the plates by the existing vacuum blowers is examined. As a result of inadequate performance and special test data it was decided to redesign the system to accommodate an Apollo RCS engine.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: The 1983 NASA(ASEE Summer Faculty Fellowship Research Program Research Reports; 15 p
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 84
    facet.materialart.
    Unknown
    Some applications of Lie groups in astrodynamics (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Differential equations that arise in astrodynamics are examined from the standpoint of Lie group theory. A summary of the Lie method is given for first degree differential equations. The Kepler problem in Hamiltonian form is treated by this method. Extension of the Lie method to optimal trajectories is outlined.
    Keywords: ASTROPHYSICS
    Type: NASA. Johnson (Lyndon B.) Space Center The 1983 NASA/ASEE Summer Faculty Fellowship Research Program Research Reports; NASA. Johnson (Lynd
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 85
    facet.materialart.
    Unknown
    Jet array impingement heat transfer characteristics (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Two dimensional arrays of circular air jets impinging on a heat transfer surface parallel to the jet orifice plate are considered. The jet flow, after impingement, is constrained to exit in a single direction along the channel formed by the jet orifice plate and the heat transfer surface. In addition to the crossflow which originates from the jets following impingement, an initial crossflow is present which approaches the array through an upstream extension of the channel. The configurations considered are intended to model the impingement cooled midchord region of gas turbine airfoils in cases where an initial crossflow is also present. A major objective is determination of the effect of initial crossflow air temperature relative to jet array air temperature on impingement surface heat fluxes.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center Turbine Eng. Hot Sect. Technol. (HOST); p 117-128
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 86
    facet.materialart.
    Unknown
    Coolant passage heat transfer with rotation. A progress report on the computational aspects (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Turbine airfoils are subjected to increasingly higher heat loads which escalate the cooling requirements in order to satisfy life goals for the component materials. If turbine efficiency is to be maintained, however, cooling requirements should be as low as possible. To keep the quantity of cooling air bounded, a more efficient internal cooling scheme must be developed. One approach is to employ airfoils with multipass cooling passages that contain devices to augment internal heat transfer while limiting pressure drop. Design experience with multipass cooling passage airfoils has shown that a surplus of cooling air must be provided as a margin of safety. This increased cooling air leads to a performance penalty. Reliable methods for predicting the internal thermal and aerodynamic performance of multipass cooling passage airfoils would reduce or eliminate the need for the safety margin of surplus cooling air. The objective of the program is to develop and verify improved analytical methods that will form the basis for design technology which will result in efficient turbine components with improved durability without sacrificing performance. The objective will be met by: (1) establishing a comprehensive experimental data base that can form the basis of an empirical design system; (2) developing computational fluid dynamic techniques; and (3) analyzing the information in the data base with both phenomenological modeling and mathematical modeling to derive a suitable design and analysis procedure.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center Turbine Eng. Hot Sect. Technol. (HOST); p 111-116
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 87
    facet.materialart.
    Unknown
    Pair production in superstrong magnetic fields (1983)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The production of electron-positron pairs by single photons in magnetic fields 10 to the twelth power G was investigated in detail for photon energies near threshold as well as for the asymptotic limit of high photon energy. The exact attenuation coefficient, which is derived and then evaluated numerically, is strongly influenced by the discrete energy states of the electron and positron. Near threshold, it exhibits a sawtooth pattern as a function of photon energy, and its value is significantly below that predicted by the asymptotic expression for the attenuation coefficient. The energy distributions of the created pair are computed numerically near threshold and analytic expressions are derived in the asymptotic limit. These results indicate that as field strength and photon energy increase, it becomes increasingly probable for the pair to divide the photon energy unequally. This effect, as well as the threshold behavior of the attenuation coefficient, could have important consequences for pulsar models.
    Keywords: ASTROPHYSICS
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 88
    facet.materialart.
    Unknown
    Introductory Comments on Stellar Atmospheric Structure and Its Modeling (1983)
    In:  CASI
    Details
    Publication Date: 2014-09-10
    Description: A general historical perspective on stellar atmospheric models is presented. Some comments on the priori speculative-theoretical modeling of the star, its atmosphere, and its environment are made. In contrast to this more speculative type of investigation, an empirical-theoretical program is defined. The objectives of the program are to delineate atmospheric structural patterns, properties of the local stellar environment, and some necessary characteristics of subatmospheric structure as inferred from the observations of nonthermal fluxes and phenomena, and thermodynamic self consistency.
    Keywords: ASTROPHYSICS
    Type: Stellar Atmospheric Struct. Patterns; p 3-18
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 89
    facet.materialart.
    Unknown
    A Study of Accretion in Compact Sources: Disk Precession and Jet Helicity (1983)
    In:  CASI
    Details
    Publication Date: 2014-09-11
    Description: The effect of adiabatic expansion on the propagation and growth of helical twisting on a supersonic jet is investigated. Cooling of the jet material increases the jet's Mach number and increases the jet's density relative to that of the external medium. This has the effect of decreasing the maximum rate of growth and increasing the maximally unstable wavelength relative to the jet's radius. Propagation effects cause the wavelength of helical waves to change at a rate different from that of the maximally unstable wavelength with the result that the characteristic wavelength of helical twisting is not equal to this wavelength. The most rapidly growing helical wave will have a wavelength as much as a factor of 2 different from the instantaneous maximally unstable wavelength.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Res. Rept.: 1983 NASA(ASEE Summer Faculty Fellowship Program; 39 p
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 90
    facet.materialart.
    Unknown
    A Numerical Investigation of the Multiple Vortex Phenomenon: Vortex Number and Structure as a Function of Swirl Ratio (1983)
    In:  CASI
    Details
    Publication Date: 2014-09-12
    Description: A numerical investigation of the multiple vortex phenomenon (MVP) for tornado like flows is conducted to determine the conditions for when a vortex becomes unstable and divides into smaller subsidiary vortices, as well as to determine the structure of these vortices. A three dimensional numerical model developed by Rotunno (1983) is utilized which has been demonstrated to successfully simulate MVP with properties observed both in natural as well as laboratory tornado like vortices. The MVP is generated for several swirl ratio conditions in order to determine the number of vortices generated for those flow configurations. These results are then compared to experimental measurements to validate the numerical model. The number of vortices produced is consistent with observational results made in the Purdue tornado vortex chamber. Furthermore, horizontal and vertical cross sections are taken through the vortices to determine the structure of MVP. Preliminary results indicate that tangential velocities within these smaller asymmetric vortices increase by 20% over values observed in a single axisymmetric vortex at the same swirl ratio.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Alabama Univ. Res. Rept.: 1983 NASA(ASEE Summer Faculty Fellowship Program; 28 p
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 91
    facet.materialart.
    Unknown
    Molecular self-shielding in the outflows from late-type stars (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: It is proposed that molecules, especially CO and H2, in the circumstellar outflows from late-type stars can be self-shielded from ambient interstellar UV radiation. The theory of self-shielding in spherical, expanding envelopes is developed for the case in which the photodestruction is dominated by absorption in the Doppler cores of the relevant UV lines, and it is shown that this theory can account for the observations of IRC plus 10216. Also considered is the case in which photodestruction takes place in the damping wings of the UV lines as is appropriate for H2. It is found that most of the hydrogen remains molecular, although the amount of atomic hydrogen is not completely negligible.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 264
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 92
    facet.materialart.
    Unknown
    On scaling the magnetic field strength in interstellar clouds Resolution of the 'B versus n dilemma' (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Attention is given to the 'B versus n dilemma' associated with the near constancy of magnetic field strength based on H I Zeeman data over a range of gas densities. The problem is examined in terms of preferential mass flow along magnetic field lines resulting from the low thermal energy of these regions. Approximate relations have been found to scale the magnetic field strength in interstellar clouds. It is noted that the fiducial gas density for scaling the increasing magnetic field strength is 2-3 orders of magnitude above the average interstellar density often used to estimate B.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 264
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 93
    facet.materialart.
    Unknown
    Evolutionary effects of helium diffusion in population II stars (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Evolutionary calculations continuing until well past turnoff are presented for models of low-mass Population II stars which take into account the effects of the diffusion of helium relative to hydrogen. Evolutionary tracks, cluster isochrones and hydrogen distributions were obtained for stellar masses in the range 0.75 to 1.01 solar masses, both in the presence and absence of diffusion. It is found that for a star of a given mass, diffusion speeds up the evolutionary process on the main sequence, although after turnoff evolution is slowed with respect to the case without diffusion. As the stars ascend the red giant branch, their outer regions are remixed so that evidence of helium diffusion is erased, and the evolutionary tracks of the models with and without diffusion converge. Thus, if the age of a globular cluster is determined from the absolute magnitude at turnoff or from fitting isochrones, diffusion results in a 25% reduction in the derived age at a turnoff magnitude of 4.23, and a 14% reduction at a turnoff magnitude of 3.45.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 264
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 94
    facet.materialart.
    Unknown
    The absence of rapid X-ray variability in active galaxies (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: (Previously announced in STAR as N82-30204)
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 264
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 95
    facet.materialart.
    Unknown
    A comparative study of time-marching and space-marching numerical methods (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Menees (1981) has conducted an evaluation of three different flowfield codes for the Jupiter entry conditions. However, a comparison of the codes has been made difficult by the fact that the three codes use different solution procedures, different computational mesh sizes, and a different convergence criterion. There are also other differences. For an objective evaluation of the different numerical solution methods employed by the codes, it would be desirable to select a simple no-blowing perfect-gas flowfield case for which the turbulent models are well established. The present investigation is concerned with the results of such a study. It is found that the choice of the numerical method is rather problem dependent. The time-marching and the space-marching method provide both comparable results if care is taken in selecting the appropriate mesh size near the body surface.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA Journal; 21; Jan. 198
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 96
    facet.materialart.
    Unknown
    Broad emission lines of QSOs are consistent with rotating supermassive stars (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The basic properties of broad emission-line profiles from quasars and Seyfert galaxies are suggested to indicate emissions originating from the surface of a rotating supermassive star. The areal extent of the ionizing luminosity and its energy are calculated, showing that the broad-line region has a mass of about 10 solar masses and a volume filling factor of 1/1,000,000. It is shown that if the broad-line region consists of a layer of ionized gas on the surface of a rotating supermassive star with an equatorial speed of 5,000 km/sec and a relatively cool surface, a layer of photoionized gas will result and emit a line emission per unit area that is proportional to the incident flux of ionizing radiation. The emitting layer will be heated to about 100 million K by an X ray component of a nonthermal continuum over a 10,000 K surface.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 305; Sept. 29
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 97
    facet.materialart.
    Unknown
    On the structure of wall-bounded turbulent flows (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The variable-interval time-averaging (VITA) technique developed by Blackwelder and Kaplan is applied to data obtained from large-eddy simulation of turbulent channel flow in an investigation of the organized structures associated with the bursting phenomenon in the near-wall region. Conditionally averaged velocities, shear stress, pressure, and vorticity are discussed in conjunction with the bursting phenomenon detected by the VITA technique. The conditionally averaged pressure reveals that the ejection process is associated with a localized adverse pressure gradient. In the plane perpendicular to the flow direction, the conditionally averaged vorticity field indicates that a pair of counterrotating streamwise vorticity is being lifted through the ejection process. Previously announced in STAR as N83-17832.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Physics of Fluids (ISSN 0031-9171); 26; Aug. 198
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 98
    facet.materialart.
    Unknown
    A study of H-alpha velocities in NGC 1499, NGC 7000, and IC 1318B/C (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Multiple slit echelle spectrograph observations of the H-alpha emission line are used to map the radial velocities of the California Nebula (NGC 1499), the North American Nebula complex (NGC 7000 and IC 5070), and IC 1318B/C. The California Nebula is singularly constant in velocity, considering its geometry. The North American Nebula complex reflects a very simple, classical dynamical picture. The expansion discovered earlier in IC 1318B/C is confirmed, detailed, and the model refined. The new data, along with that in earlier papers of this series, show that stellar wind acceleration and champagne flow mechanisms both play important roles in determining the evolution of H II regions.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 269; June 1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 99
    facet.materialart.
    Unknown
    Coherent structures - Reality and myth (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Large-scale coherent structures (CS) in turbulent shear flows are characterized, reviewing recent theoretical and experimental investigations. The use of computers as a research tool and the flow-visualization experimental technique are introduced, CS are defined, the history of their discovery is traced, and their main characteristics are listed. Topics discussed and illustrated include the initial condition of the free shear layer, triple and double decomposition, topological features of CS, detection and eduction of CS, phase alignment via cross correlation, induced versus natural structures, the bursting phenomenon, turbulent spot, streaks, bursting frequency, the axisymmetric mixing layer, vortex pairing in an axisymmetric jet, CS and jet noise, broadband noise amplification via pure-tone excitation, CS interaction in a plane-jet near field, the Taylor hypothesis applied to CS, negative production, and the validity of the Reynolds-number similarity hypothesis. It is found that the coherent Reynolds stress, vorticity, and production are not much greater than the time-averaged values for fully developed flows with significant incoherent turbulence, suggesting that the importance of CS may have been exaggerated in some recent studies.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Physics of Fluids (ISSN 0031-9171); 26; 2816-285
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 100
    facet.materialart.
    Unknown
    Dust in galaxies (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The manifestations of dust in the Galaxy, in normal galaxies, active nuclei galaxies (ANGs), and in QSOs are discussed. Findings on the composition, abundance, size distribution, and global properties of the Galaxy's dust obtained with absorption and emission studies are reviewed. The properties of dust in other galaxies, the variation of those properties among galaxies, and the effect of the dust on the appearance of galaxies are considered, discussing the LMC, M51, and M82 as examples. Evidence for the existence of dust in the nuclei of ANGs and in QSOs is examined with regard to reddening, dust emission and absorption, and polarization. The question of the existence of intergalactic dust is briefly addressed.
    Keywords: ASTROPHYSICS
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...