June 2013

Issue 55



Atmospheric Aerosols Meeting (reminder)


The Optical Characterization of Atmospheric Aerosols workshop will take place at the Congress Centre Smolenice SAS, Slovak Republic in November 5-7 2013.


The main goal of the workshop is to present an opportunity for scientists in different fields to meet and form efficient collaborations in the research of atmospheric aerosols, including aerosol characterization, remote sensing, instrumentation, and optical modeling. Abstract submission due is June 30, 2013.


Meeting website is http://www.ocaa2013.sav.sk/



ADDA new version (1.2) has been released


Below the most important changes in this release are summarized. For a more detailed list please see

http://code.google.com/p/a-dda/wiki/ReleaseNotes .


* Sparse mode is now fully integrated into ADDA and significantly improved. It is designed for very porous particles.

* Linked to new OpenCL FFT library from AMD, it is now the default one in OpenCL mode. Speed improvement is a few times depending on the GPU.

* New iterative solver BCGS2 - an improved version of BICGSTAB.

* New command line option argument '-init_field read <filenameY> [<filenameX>]' to initialize an iterative solver by the field read from file.

* Finally removed deprecated options -Cpr_mat and '-sg_format ddscat'.

* Several wiki pages were added and documentation was improved.

* Several improvements to Makefile.


You are advised to upgrade to a new version, which can be downloaded (both main package and, if needed, executable for 32- and 64-bit Windows) from: http://code.google.com/p/a-dda/downloads/


Finally, please note that ADDA is an open-source project which development relies on the community around it. There are many ways to help:

* Using ADDA and advocating its use through publications and conference presentations.

* Active participation in the discussion group - http://groups.google.com/group/adda-discuss, in particular, sharing your experience with other users.

* Commenting and improving wiki pages ( http://code.google.com/p/a-dda/w/list ) and other documentation.

* Locating bugs and proposing new features for ADDA, using the issue tracker - http://code.google.com/p/a-dda/issues .

* Contributing and improving the source code - http://code.google.com/p/a-dda/wiki/InstructionCommitters .


Best regards,

Maxim Yurkin.



DDSCAT 7.3.0

New release of the discrete-dipole approximation scattering code


DDSCAT 7.3.0 adds new capabilities, and corrects a few bugs in the previous release (DDSCAT 7.2.2) that affected a few applications.


New Features

1. DDSCAT 7.3.0 can now efficiently calculate both E and B throughtout a user-specified rectangular volume containing the target. The polarization P, and nearfield E (and B, if desired) are saved as files. The nearfield volume, and whether to calculate and store B as well as E, is easily specified in the parameter file ddscat.par .

2. DDSCAT 7.3.0 includes the "Filtered Coupled Dipole" method as an option that can be selected by the user.

3. DDSCAT 7.3.0 can now use and store results for up to 10^6 target orientations. (For some applications, at least one user wanted more than the previous limit of 10^3 orientations.)

4. DDSCAT 7.3.0 now reports the *macroscopic* E field within the target, rather than the "microscopic" E field as in the past. (The relationship between the macroscopic and microscopic fields is explained in the UserGuide.)

5. The DDSCAT 7.3.0 distribution includes a separate F90 code, DDPOSTPROCESS.f90, designed to read the stored P and E (and B) and perform postprocessing calculations (e.g., calculating the Poynting flux). DDPOSTPROCESS.f90 can be modified by the user to do additional postprocessing calculations, or to output results in other formats.

6. As with DDSCAT 7.2.2, the DDSCAT 7.3.0 distribution includes VTRCONVERT.f90 to support visualization of the target geometry using the Visualization Toolkit (VTK) and ParaView.


All of these features are described in the UserGuide.


Bug Fixes. DDSCAT 7.3.0 corrects the following problems in 7.2.2:

1. DDSCAT 7.3.0 should now be able to correctly calculate absorption and scattering for incident waves with arbitrary elliptical polarizations.

2. DDSCAT 7.3.0 corrects bugs that affected some calculations using OpenMP.

3. Calculations with anisotropic targets were affected by a bug in subroutine unreduce.f90. This has been corrected.


Obtaining DDSCAT 7.3.0

The complete DDSCAT 7.3.0 package can be downloaded from http://code.google.com/p/ddscat

The code distribution (including the UserGuide) is in the gzipped tarfile ddscat7.3.0_130326.tgz

You can also download the set of "worked examples" that are referred to in the UserGuide: ddscat7.3.0_examples_130326.tgz

Windows executables can be downloaded from http://code.google.com/p/ddscat/wiki/Windows (this should be available in the near future).

DDSCAT 7.3 is gratis, subject to the GNU General Public License. [You may copy, distribute, and/or modify the software identified as under this agreement. If you distribute copies of this software, you must give the recipients all the rights that you have.]

As always, please let us know if you encounter problems downloading DDSCAT, or if you have trouble using DDSCAT (but **please** read the manual carefully, and try running the examples, before reporting problems!!).


Version 7.2 is no longer supported, although it will continue to be available on the google code site. If you have been using Version 7.2 (or an earlier version) please switch to Version 7.3.

We hope that DDSCAT 7.3 will prove useful in your research. If you publish papers using DDSCAT 7.3, please cite

1. Draine, B.T., & Flatau, P.J. 1994, "Discrete dipole approximation for scattering calculations", JOSA A, 11, 1491-1499 and relevant papers describing the DDA and its implementation in DDSCAT, e.g.,

2.Goodman, J.J., Draine, B.T., & Flatau, P.J. 1991, "Application of FFT Techniques to the Discrete Dipole Approximation", Optics Letters, 16, 1198-1200

3. Draine, B.T., & Flatau, P.J. 2008, "Discrete-dipole approximation for periodic targets: theory and tests", JOSA A, 25, 2693-2703

4. Flatau, P.J., & Draine, B.T. 2012, "Fast near-field calculations in the discrete dipole approximation on regular rectilinear grids", Optics Express, 20, 1247-1252



See recently indexed and summarized papers on the optics of particles and dispersions in TPDSci: http://www.tpdsci.com/Sv_.phplist=SvPdo


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