February 2008 ISSUE 24
Meetings
The 11th Conference on Electromagnetic and Light
Scattering
7-12 September 2008
Second Announcement
Registration
is now open for the 11th Conference on Electromagnetic and Light Scattering to
be held at the
This conference falls in the year of the centenary celebration of the publication of an epoch-making paper in scattering theory by Gustav Mie. It will bring together scientists and engineers from around the world who are actively involved in research into light scattering and will address theoretical developments and simulations, laboratory and field experiments, measurements and applications.
The
conference dinner, an Elizabethan banquet, will be
held at Hatfield House which was previously home to Elizabeth I of
For further information see http://www.els-xi-08.org . Please note that some deadlines, for example - applications for grants, have been extended.
James Hough and Paul Kaye
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New Papers
Y.Okada, "Efficient numerical orientation averaging of light scattering properties with a quasi-Monte-Carlo method", JQSRT, accepted.
http://dx.doi.org/10.1016/j.jqsrt.2008.01.002
Abstract We studied numerical orientation averaging with three methods for selection of orientations: lattice-grid division, crude Monte-Carlo method (CMC), and quasi-Monte-Carlo method (QMC). Numerical orientation averaging with these methods was carried out with a fixed orientation version of the T-matrix method for clusters of spheres. The errors of numerical orientation averaging as a function of number of orientations are investigated by comparison with results from analytical orientation averaging of the T-matrix method. We studied 4 types of aggregates: a bisphere, ballistic cluster-cluster aggregates of 4 and 128 monomers (BCCA4 and BCCA128), and a ballistic particle-cluster aggregate of 128 monomers (BPCA128). We studied convergence of the scattering efficiency $Q_{sca}$, absorption efficiency $Q_{abs}$, asymmetry parameter $g$, intensity $4 S_{11}/x_v^2$, and degree of linear polarization $P=-S_{12}/S_{11}$. For the polarization, scattering angles of maximum ($Theta_{max}$) and minimum ($Theta_{min}$) polarization in results of analytical orientation averaging are considered. For the intensity, in addition to $Theta_{max}$ and $Theta_{min}$, forward
scattering angle ($Theta=10$$^circ$) is also considered.
Y.Okada, I.Mann, I.Sano, S.Mukai, "Acceleration of the iterative solver in the discrete dipole approximation: Application to the orientation variation of irregularly shaped particles", JQSRT, accepted. http://dx.doi.org/10.1016/j.jqsrt.2008.01.004
Abstract We have applied a method of reducing the number of iterations required to solve a system of linear equations in the discrete dipole approximation. This method obtains an initial guess of dipole polarization from those with similar particle characteristics (e.g., the size parameter and refractive index) calculated a priori. If the initial guess is closer to the solution, the number of iterations of the linear equation solution becomes smaller than that calculated with an arbitrary initial value. This method was applied to various particle orientations using spline interpolation of the initial guess of dipole polarization from orientations calculated a priori. We studied three types of particle model: an aggregate, a deformed sphere with moderate surface roughness, and a particle with a large number of edges. For the particle with a large number of edges, we propose a new model called the overlapping mixture of multiple tetrahedra (OMMT). The proposed method is most advantageous for particles with moderate surface roughness (e.g., a deformed sphere), for which the calculation time was reduced to 20-40% of the original calculation time. For OMMT and an aggregate, the computation time was reduced to 30-60% and 40-90%, respectively. The differences in the scattering coefficient, absorption coefficient, intensity and polarization introduced by our method were lessthan 0.008%, 0.03%, 0.1%, and 0.08%, respectively. If the light scattering properties vary slowly with the orientation variation, interpolation of the results is more efficient than the proposed method and produces only a small difference in the results. However, theinterpolation of the results fails for particles such as BCCA64, for which our proposed method produces more accurate results.