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日時：	2011年10月20日（木）　14:00-15:30
場所：	九州大学　応用力学研究所６階セミナー室（W606）
講演者：	Prof. Anatoli Borovoi Institute of Atmospheric Optics Russian Academy of Sciences Tomsk-city, Russia
題目：	Light scattering by large nonspherical particles
要旨：	The problem of light scattering by nonspherical particles is a challenging problem of the atmospheric optics. If scattering particles are less than the wavelength of the incident electromagnetic wave, the problem is solved by a number of numerical methods like the FDTD (finite-difference time-domain method), the DDA (discrete dipole approximation) , etc.     These methods turn out to be computationally cost if particle sizes exceed the incident wavelength more than, say, 10 times. In this case, an opposite approach based on geometric optics becomes reasonable. Here numerical algorithms using ray-tracing technique are widely used. However, the solutions obtained by the ray-tracing have a difficulty to take into account the wave properties of light.     In our approach we overcome these difficulties by use of the basic concepts of the physical optics, i.e. by including diffraction and interference. We show that these concepts are easily introduced if, on the first step, the scattered field is considered in the near zone. Then the near-zone electromagnetic field is transformed into the desired far-zone field by the well-known exact integral transformation. We demonstrate an advantage of such an approach on the practically important task of light scattering by ice crystal particles of cirrus clouds.

連絡先：岡本創