Thank you very much, Derek:).
I think that it is preferable to use the subdomain id of each element for represnting the corresponding material property. However, the materail property of boundary is difficult to be represented. I can't find some examples reading boudary information from certain file formats, such as .unv, .xda and so on. I can't also find a data structure for boudary information. I think that boundary information is important. Whether does the information affect the parallel implementation? 
I am beginning to learn of libmesh. I have not a  better idea for this problem. I will further learn of it. If I have, I will post them. 
Thanks a lot.

On 8/28/07, Derek Gaston <> wrote:
Hmmm... this seems to be getting more attention lately... maybe we
should think about putting in a proper material database

Yujie, to answer your question, there are a few ways to do material
properties.  You can use the subdomain id of each element to specify
which elements have which material on them.  In this case you have to
check the subdomain of each element as you assemble your matrix and do
the material property calculation yourself.  This will be necessary if
you want some non-linear property for instance.

You could also use the MeshData class to store a material property per
element (such as a per element conductivity or whatever).  But, of
course this only works for simple scalar properties that are constant
on an element.

In general we don't really have a great way of doing material
properties.  If you have some ideas I'd be interested in hearing them.
Doing something general enough that it will be useful to multiple
people will definitely be a challenge...


On 8/27/07, Yujie Lv <> wrote:
> Hi everyone,
> I have browsed the examples about libmesh. However, I can't find some
> examples about solving a PDE in a domain with different materials.
> Futhermore, Cauchy or neumann boundary conditions are not considered. I want
> to know whether the mesh structure can support the representation of
> different materials, including in domain and surface?
> thanks a lot.
> Regards,
> Yujie
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