Characterization of complex systems from inverse radiative transfer measurements

Summary Starting from a characterization of radiative transfer in terms of a collision rate λ and a single-collision transition probability Ψ, we study the distribution of the generalized state ζ(t) of a radiation particle at time t conditional on a specified initial state at time t = 0. The generalized state is a vector consisting of the state ω(t) at time t and the states ω 1, ω 2, …, ω n of the particle immediately after the collisions it experiences in the time interval (0, t]. The variable ζ(t) takes values in a population space and can be studied conveniently with the aid of a certain generating functional G. The first-collision integral equation and the backward integro-differential equation for G are derived. Simultaneous consideration of the first-collision and last-collision equations lead to a generalized reciprocity principle for G. First-passage problems are also considered. Finally a number of illustrative examples are given.

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Opacity distribution functions for stellar spectra synthesis

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935723 ◽

2019 ◽

Vol 627 ◽

pp. A157

Author(s):

M. Cernetic ◽

A. I. Shapiro ◽

V. Witzke ◽

N. A. Krivova ◽

S. K. Solanki ◽

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Keyword(s):

Radiative Transfer ◽

Spectral Synthesis ◽

Distribution Functions ◽

Transmission Curve ◽

Spectral Interval ◽

Space Telescopes ◽

Radiative Fluxes ◽

Stellar Spectra ◽

Speed Up

Context. Stellar spectra synthesis is essential for the characterization of potential planetary hosts. In addition, comprehensive stellar variability calculations with fast radiative transfer are needed to disentangle planetary transits from stellar magnetically driven variability. The planet-hunting space telescopes, such as CoRoT, Kepler, and TESS, bring vast quantities of data, rekindling the interest in fast calculations of the radiative transfer. Aims. We revisit the opacity distribution functions (ODF) approach routinely applied to speed up stellar spectral synthesis. To achieve a considerable speedup relative to the state of the art, we further optimize the approach and search for the best ODF configuration. Furthermore, we generalize the ODF approach for fast calculations of flux in various filters often used in stellar observations. Methods. In a parameter-sweep fashion, we generated ODF in the spectral range from UV to IR with different setups. The most accurate ODF configuration for each spectral interval was determined. We adapted the wavelength grid based on the transmission curve for calculations of the radiative fluxes through filters before performing the normal ODF procedure. Results. Our optimum ODF configuration allows for a three-fold speedup, compared to the previously used ODF configurations. The ODF generalization to calculate fluxes through filters results in a speedup of more than two orders of magnitude.

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Preparation and characterization of a series of porous anion-exchanger chelating fibers and their adsorption behavior with respect to removal of cadmium(ii)

RSC Advances ◽

10.1039/c6ra21713c ◽

2016 ◽

Vol 6 (116) ◽

pp. 115222-115237 ◽

Cited By ~ 3

Author(s):

Mingqiang Liu ◽

Zhongan Tao ◽

Huicai Wang ◽

Fei Zhao ◽

Qiang Sun

Keyword(s):

Complex Systems ◽

Anion Exchanger ◽

High Salt ◽

Adsorption Behavior ◽

Salt Complex ◽

Salt Systems

The aim of the present study was to investigate a series of porous anion-exchanger chelating fibers (PP-g-AA-Am), prepared using polypropylene (PP) for the removal of Cd(ii) in non-salt systems and in high-salt complex systems.

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