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L. Crivellari U. Flora M. Mercanti C. Morossi L. Rusconi G. Sedmak 《Astrophysics and Space Science》1981,80(2):425-436
We present an identification list for the visible spectra of three B stars: π Cet (B7V), 36 Lyn B8 IIIp (?)),and 134 Tau (B9 IV). Equivalent widths have been measured on medium dispersion plates (7.0 and 12.4 Å mm?1) taken with the 152 cm coudé reflector at the Observatoire de Haute Provence (France). These results are also presented. The photographic plates were digitized by using a PDS 1010A microdensitometer. The spectroscopic data were reduced by means of a dedicated software package and an attempt was made to compute equivalent widths in a homogeneous way. T eff and logg parameters were estimated by using the computer to compare automatically the spectroscopic data with the value of theoretical models. 相似文献
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Ghorbanzadeh Omid Shahabi Hejar Crivellari Alessandro Homayouni Saeid Blaschke Thomas Ghamisi Pedram 《Landslides》2022,19(4):929-939
Landslides - Recent landslide detection studies have focused on pixel-based deep learning (DL) approaches. In contrast, intuitive annotation of landslides from satellite imagery is based on... 相似文献
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R. J. García López R. Rebolo L. Crivellari J. E. Beckman 《Astrophysics and Space Science》1990,169(1-2):109-111
Precise photometric observations of stars in the double cluster h and Persei reveal a large spread in the colours and magnitudes of the upper Main-Sequence; half of the stars are variables that are Be stars or related stars. The reported age difference between both clusters is found to be spurious. Rotation apparently affects both the intrinsic and the observed colours of the early-type stars in h and Persei. This result questions the validity of photometric calibrations that heavily rely on h and Persei or similar clusters.Paper presented at the 11th European Regional Astronomical Meeting of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain. 相似文献
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Radiative transfer (RT) problems in which the source function includes a scattering-like integral are typical two-points boundary
problems. Their solution via differential equations implies making hypotheses on the solution itself, namely the specific
intensity I (τ; n) of the radiation field. On the contrary, integral methods require making hypotheses on the source function S(τ). It seems of course more reasonable to make hypotheses on the latter because one can expect that the run of S(τ) with depth is smoother than that of I (τ; n). In previous works we assumed a piecewise parabolic approximation for the source function, which warrants the continuity
of S(τ) and its first derivative at each depth point. Here we impose the continuity of the second derivative S′′(τ). In other words, we adopt a cubic spline representation to the source function, which highly stabilizes the numerical
processes. 相似文献
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Once the need for an iterative procedure in order to solve the problem of the formation of spectral lines in the case of a model atom with many energy levels, the sequel is to seek for the most effective form of such an iterative scheme. It is an almost universal is assumed within all the iterative methods for the solution of those radiative transfer problems, in which the transfer equations are coupled to the state of the matter, to take as the input of each step of iterations the values of the opacity coefficients obtained as a result of the previous one. This is, for instance, the procedure used to correct the temperature in the computation of stellar atmosphere models, or that to build the -operator (either the exact or the approximated one) within the Accelerated Lambda Iteration methods. Yet, if we assume, in order to solve the multilevel line transfer problem, that at each step of iterations the line opacities are known, we can express via the statistical equilibrium equations the populations of the energy levels - and consequently the source functions of the relevant spectral lines - as a linear function of the full set of the corresponding mean intensities of the radiation field. Once such linear forms for the source functions, we are able to solve without the need of any further approximation the radiative transfer equations for are obtained lines, now linearly coupled through the above linear forms of the statistical equilibrium equations. This is achieved by means of the Implicit Integral Method that we already presented in a series of previous papers. 相似文献
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