@nm 

Do you know some references out of Maple? Articles, books..

@nm 

Analytical??

Can you give me some references??

Tks!

@nm  thanks for your Support.

But the second equation ist Not a pde!

Which numerical method the maple use?

Thanks every one!

@dharr gave the more easy solution to me! I just did  a small modification

for i from 0 to 20 by 0.1 do #small step
  fprintf(out,"%f  %f\n", i, eval(res,t=i)):
od:
fclose(out);

@Rouben Rostamian  

You have make a great job! But you don't put the fourier boundary condition (see at picture at first post).

@acer 

Very thanks!!

it's a big surprise (to me) that changing one letter can make the program stop working!

Very thanks Mr. Rouben Rostamian

I am use maple 13. Yours conde do not work.....