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  • Astrophysics  (4)
  • Space Radiation  (2)
  • Turbulence Model  (1)
  • 1
    Digitale Medien
    Digitale Medien
    Numerical predictions of flows over backward-facing steps (1984)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 4 (1984), S. 711-724 
    Details
    ISSN: 0271-2091
    Schlagwort(e): Finite-Volume Method ; Numerical Diffusion ; Upstream Weighted Differencing ; Skew Upstream Differencing ; Turbulent Recirculating Flow ; Turbulence Model ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: Predictions are reported for two-dimensional, steady, incompressible flows over rearward-facing steps for both laminar and turbulent conditions. The standard k-∊ turbulence model was used for the turbulent flow. Attention was focused on obtaining accurate solutions to the differential equations. It is concluded that some of the serious discrepancies that have occurred between prediction and observation, and attributed in earlier studies to the inadequacy of the turbulence model, may have been due to the inaccuracy of the solution.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/fld.1650040802
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  • 2
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    Evidence for COMPTEL detections of low-energy gamma rays from HVC complexes (1997)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: Observational evidence of extended MeV emissions that may be associated with high velocity clouds (HVCs) is reported on. Based on observations acquired between 1991 and 1996 with the Compton telescope (COMPTEL), evidence is found for intense gamma ray radiation at 0.75 to 3 MeV from the general direction of two HVC regions. One bright gamma ray excess is located between the HVC complexes M and A, adjacent to the Lockman hole and is seen to approximately cover a sky area of exceptionally low H I column densities. A second source is detected at the high velocity end of complex C near the Draco Nebula. Both gamma ray excesses appear to consist of a time variable source and a diffuse emission component. The enhanced diffuse soft X-rays seen by Rosat from both HVC regions may be closely related to the gamma ray emission in terms of bremsstrahlung arising from HVC interactions with the galactic disk or lower halo.
    Schlagwort(e): Space Radiation
    Materialart: Proceedings of 2nd INTEGRAL Workshop 'The Transparent Universe'; 119-122; ESA-SP-382
    Format: text
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  • 3
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    Propagation of Light Elements in the Galaxy (2003)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-18
    Beschreibung: The origin and evolution of isotopes of the lightest elements d, He-3, Li, Be, and B in the universe is a key problem in such fields as astrophysics of CR, Galactic evolution, non-thermal nucleosynthesis, and cosmological studies. One of the major sources of these species is spallation by CR nuclei in the interstellar medium. On the other hand, it is the Boron/Carbon ratio in CR and Be-10 abundance which are used to fix the propagation parameters and thus spallation rate. We study production and Galactic propagation of these species using the numerical propagation code GALPROP and updated production cross sections.
    Schlagwort(e): Astrophysics
    Materialart: 28th ICRC; Jul 31, 2003 - Aug 07, 2003; Japan
    Format: text
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  • 4
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    A New Estimate of the Extragalactic Gamma-ray Background from EGRET Data (2003)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-18
    Beschreibung: We use the GALPROP model for cosmic-ray propagation to obtain our best prediction of the Galactic component of gamma rays, and show that away from the Galactic plane it gives an accurate prediction of the observed Energetic Gamma Ray Experiment Telescope (EGRET) intensities. On this basis we re-evaluate the isotropic extragalactic gamma-ray background. We find that for some energies previous work underestimated the Galactic contribution and hence overestimated the background. Our new background spectrum shows a positive curvature similar to that expected for models of the extragalactic emission based on the blazar population.
    Schlagwort(e): Space Radiation
    Materialart: 28th ICRC Meeting; Jul 31, 2003 - Aug 07, 2003; Japan
    Format: text
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  • 5
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    Propagation Model for Cosmic Ray Species in the Galaxy (2002)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-18
    Beschreibung: During the last decade there have been a number of space and balloon experiments with improved sensivity and statistics, which impose stricter constraints on cosmic ray propagation models. Propagation is the main issue in the interpretation of such data as antiproton and positron fluxes in cosmic rays, and diffuse gamma-ray emission. We develop a new propagation model that reproduces measurements of secondary antiprotons as well as primary and secondary nuclei. We will present results of our calculation of CR propagation in the Galaxy for this model using the GALPROP code.
    Schlagwort(e): Astrophysics
    Format: text
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  • 6
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    Detailed Investigation of the Gamma-Ray Emission in the Vicinity of SNR W28 with FERMI-LAT (2014)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: We present a detailed investigation of the Gamma-ray emission in the vicinity of the supernova remnant (SNR) W28 (G6.40.1) observed by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. We detected significant -ray emission spatially coincident with TeV sources HESS J1800240A, B, and C, located outside the radio boundary of the SNR. Their spectra in the 2-100 GeV band are consistent with the extrapolation of the power-law spectra of the TeV sources. We also identified a new source of GeV emission, dubbed Source W, which lies outside the boundary of TeV sources and coincides with radio emission from the western part of W28. All of the GeV Gamma-ray sources overlap with molecular clouds in the velocity range from 0 to 20 km s (exp1). Under the assumption that the Gamma-ray emission toward HESS J1800240A, B, and C comes from 3.14(exp0) decay due to the interaction between the molecular clouds and cosmic rays (CRs) escaping from W28, they can be naturally explained by a single model in which the CR diffusion coefficient is smaller than the theoretical expectation in the interstellar space. The total energy of the CRs escaping from W28 is constrained through the same modeling to be larger than is approximately 2 10(exp49) erg. The emission from Source W can also be explained with the same CR escape scenario.
    Schlagwort(e): Astrophysics
    Materialart: GSFC-E-DAA-TN15818 , The Astrophysical Journal; 786; 2; 145
    Format: application/pdf
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  • 7
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    Observations of the Li, Be, and B Isotopes and Constraints on Cosmic-ray Propagation (2007)
    In:  CASI
    Details
    Publikationsdatum: 2019-08-14
    Beschreibung: The abundance of Li, Be, and B isotopes in galactic cosmic rays (GCR) between E=50-200 MeV/nucleon has been observed by the Cosmic Ray Isotope Spectrometer (CRIS) on NASA's ACE mission since 1997 with high statistical accuracy. Precise observations of Li, Be, B can be used to constrain GCR propagation models. We find that a diffusive reacceleration model with parameters that best match CRIS results (e.g. B/C, Li/C, etc) are also consistent with other GCR observations. A approx. 15-20% overproduction of Li and Be in the model predictions is attributed to uncertainties in the production cross-section data. The latter becomes a significant limitation to the study of rare GCR species that are generated predominantly via spallation.
    Schlagwort(e): Astrophysics
    Materialart: To appear in Journal of Advances in Space Research
    Format: application/pdf
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