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  • ASTROPHYSICS  (189)
  • AIRCRAFT PROPULSION AND POWER  (119)
  • 1980-1984
  • 1975-1979  (308)
  • 1935-1939
  • 1979  (175)
  • 1975  (133)
  • 1
    Publication Date: 2019-06-27
    Description: A single stage compressor was designed with the intent of demonstrating that, for a tip speed and hub-tip ratio typical of an advanced core compressor front stage, the use of low aspect ratio can permit high levels of blade loading to be achieved at an acceptable level of efficiency. The design pressure ratio is 1.8 at an adiabatic efficiency of 88.5 percent. Both rotor and stator have multiple-circular-arc airfoil sections. Variable IGV and stator vanes permit low speed matching adjustments. The design incorporates an inlet duct representative of an engine transition duct between fan and high pressure compressor.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-159555 , PWA-5583-25
    Format: application/pdf
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  • 2
    Publication Date: 2019-07-13
    Description: The results of a program of experimental and analytical research in casing treatments over axial compressor rotor blade tips are presented. Circumferential groove, axial-skewed slot and blade angle slot treatments were tested at low speeds. With the circumferential groove treatment the stalling flow was reduced 5.8% at negligible efficiency sacrifice. The axial-skewed slot treatment improved the stalling flow by 15.3%; 1.8 points in peak efficiency were sacrificed. The blade angle slot treatment improved the stalling flow by 15.0%; 1.4 points in peak efficiency were sacrificed. The favorable stalling flow situations correlated well with observations of higher-than-normal surface pressures on the rotor blade pressure surfaces in the tip region, and with increased maximum diffusions on the suction surfaces. Annulus wall pressure gradients, especially in the 50 to 75% chord region, are also increased and blade surface pressure loadings are shifted toward the trailing edge for treated configurations.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: ASME PAPER 75-GT-60 , American Society of Mechanical Engineers, Gas Turbine Conference and Products Show; Mar 02, 1975 - Mar 06, 1975; Houston, TX
    Format: text
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  • 3
    Publication Date: 2006-07-16
    Description: Major solution techniques for internal computational fluid mechanics are discussed and some examples are presented. The major steps involved in developing a large computer code are then discussed.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Aeropropulsion 1979; p 187-230
    Format: text
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  • 4
    Publication Date: 2011-08-16
    Description: The Second Small Astronomy Satellite (SAS-2) high-energy (in excess of 35 MeV) gamma-ray telescope has detected pulsed gamma-ray emission at the radio period from PSR 0833-45, the Vela pulsar, as well as an unpulsed flux from the Vela region. The pulsed emission consists of two peaks following the single radio peak by about 13 ms and 48 ms. The luminosity of the pulsed emission above 100 MeV from Vela is about 0.1 that of the pulsar NP 0532 in the Crab nebula, whereas the pulsed emission from Vela at optical wavelengths is less than 0.0002 that from the Crab. The relatively high intensity of the pulsed gamma-ray emission, and the double peak structure, compared with the single pulse in the radio emission, suggest that the high-energy gamma-ray pulsar emission may be produced under different conditions from those at lower energies.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 200; Sept. 1
    Format: text
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  • 5
    Publication Date: 2011-08-16
    Description: The possibility that the origin of extinct radioactivities depended on their living long enough for grains to form in the expanding nucleosynthetic envelope, rather than on their living long enough for meteorites to form, is examined. As an example, the interpretation of Na-22 as a detectable extinct radioactivity, with a half life of only 2.6 years, is explored and related to Ne-22 occurrence. Similar arguments involving He-4, Ar-40, K-40, K-41, and calcium, titanium, chromium, manganese, iron, nickel, and cobalt isotopes are briefly presented.
    Keywords: ASTROPHYSICS
    Type: Nature; 257; Sept. 4
    Format: text
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  • 6
    Publication Date: 2011-08-16
    Description: A multiple shock system was observed upstream (0.13 AU) of the earth by Pioneer 9 on February 2, 1969. The same system was observed at earth by Ogo 5 and was reported separately in the literature. This paper compares the two sets of observations in still further detail. Both magnetic-field and plasma data are used in a least-squares best-fit method to compute the characteristics of the fast forward shock wave (Pioneer 9 only) and two fast reverse shock waves. Nearly all major features (shock, piston, and tangential discontinuity) retained their characteristics during the transit of the shock ensemble from Pioneer 9 to Ogo 5. The genesis of the ensemble is believed to be due to a complex stream-stream interaction. A substantial density increase (including a large rise of alpha/proton abundance) at Ogo 5, but unobserved at Pioneer 9, is explained by a sudden meridional shift to a flow from below the ecliptic plane while the streams were en route to earth. This study demonstrates a spatial and temporal plasma inhomogeneity which is superimposed on the persistent major features.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research; 80; Aug. 1
    Format: text
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  • 7
    Publication Date: 2011-08-16
    Description: Data are reported which were obtained with a high-energy (exceeding 35 Mev) gamma-ray telescope flown on the second Small Astronomy Satellite (SAS-2). The high-energy galactic gamma radiation is observed to dominate over the general diffuse radiation along the entire galactic plane, and its longitudinal and latitudinal distributions appear to be generally correlated with galactic structural features, particularly with arm segments. Principally on the basis of its angular distribution and magnitude, it is suggested that this radiation results primarily from cosmic-ray interactions with interstellar matter. A uniform celestial gamma radiation appears to have been detected; the form of its differential spectrum over the energy range from about 35 to 170 MeV is obtained, and a cosmological origin is suggested for this radiation. In addition to the general galactic emission, high-energy gamma radiation was detected from the Crab Nebula, Vela X, a general region toward the galactic center, and a region located a few degrees north of the galactic plane. Upper limits to the high-energy gamma ray fluxes are set for a number of localized sources.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 198; May 15
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  • 8
    Publication Date: 2011-08-16
    Description: An upper limit on the column density of C IV along the line of sight to gamma-2 Vel is derived from upper limits placed on the equivalent widths of the interstellar C IV doublet with rest wavelengths at 1548.20 A and 1550.77 A. A lower limit of 250,000 K is calculated for the electron temperature of O VI emitting regions by combining the C IV results with a measurement of the column density of interstellar O VI for the same star and using calculations for the relative ionization of some abundant elements as a function of electron temperature in a low-density plasma. Since gamma-2 Vel is in the central part of the Gum Nebula, the high temperature suggested by these results is shown to support the idea that a high-temperature phase of the interstellar medium, possibly maintained by supernova explosions, may exist.-
    Keywords: ASTROPHYSICS
    Type: The Observatory; 95; Oct. 197
    Format: text
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  • 9
    Publication Date: 2011-08-17
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 228
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  • 10
    Publication Date: 2011-08-17
    Description: HEAO-1 observations of aperiodic variability in the galactic X-ray source GX339-4 (4U 1658-48) on time scales of tens of milliseconds to a few seconds are reported. It is shown that the overall characteristics of GX339-4 place it in the same class of X-ray sources as Cyg X-1 and Cir X-1, which are candidates for black holes in binary systems. The detection of X-ray flares from GX339-4 is discussed, particularly a series of five sequential flares with separations of about 250 ms.
    Keywords: ASTROPHYSICS
    Type: Nature; 278; Mar. 29
    Format: text
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