This widget is a combo-box only active when the checkbox 
result fields is checked.
It allows to choose between three different options:
-   every n time step  : means that every n time step a complete result field will be written 
in the file having the extension ".rdt". For large mesh, choosing a too small number n (positive integer)
may induce very large files and is also quite costly in terms of CPU time. 
-    every x seconds  : means that every x seconds  a complete result field will be written 
in the file having the extension ".rdt". Again a too small value x with respect to the duration of the 
transient to be simulated, 
may induce a large number of intermediate fields (especially with the automatic time step), since interpolated fields may be generated when x is smaller 
than the time step used. 
-   time list  : corresponds to a list of instants (given in seconds - for exemple two hours and 10 hours should be indicated 7200 36000) for which complete result fields will be written in a result file having the extension ".rdt" 
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 SYRTHES version   : VERSION_SYRTHES
 Name help file  : Cb_3D_Op.html
 I. Rupp, C. Peniguel  -  may 2014
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