WolfgangGellien

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These are questions asked by WolfgangGellien

Hello, to all,
On my computer I have installed Windows 7 Professional, Maple 2018.2.1 and
Physics:-Version()[2];
 2019, January 5, 13:32 hours, version in the MapleCloud: 276,

    version installed in this computer: 276
When I try to compute some examples from your poste "PDE_and_BC_during_2018.mw", I get an error in Example 8:
Example 8: This problem represents the temperature distribution in a thin circular plate whose lateral surfaces are insulated (Articolo example 6.9.2):
pde__8 := diff(u(r, theta, t), t) = (diff(u(r, theta, t), r)+r*(diff(u(r, theta, t), r, r))+(diff(u(r, theta, t), theta, theta))/r)/(25*r);
                                       /                    
                                       |                    
                                       |                    
                                       |                    
              d                    1   |/ d                \
   pde__8 := --- u(r, theta, t) = ---- ||--- u(r, theta, t)|
              dt                  25 r |\ dr               /
                                       \                    

                                      2                  \
                                     d                   |
                                  -------- u(r, theta, t)|
          /  2                \          2               |
          | d                 |    dtheta                |
      + r |---- u(r, theta, t)| + -----------------------|
          |   2               |              r           |
          \ dr                /                          /
iv__8 := D[1]*u(1, theta, t) = 0, u(r, 0, t) = 0, u(r, Pi, t) = 0, u(r, theta, 0) = (r-(1/3)*r^3)*sin(theta);
   iv__8 := D[1] u(1, theta, t) = 0, u(r, 0, t) = 0,

                                       /    1  3\           
     u(r, Pi, t) = 0, u(r, theta, 0) = |r - - r | sin(theta)
                                       \    3   /           
pdsolve([pde__8, iv__8], u(r, theta, t), HINT = boundedseries(r = [0]));
Error, (in dsolve) cannot determine if this expression is true or false: not 0 <= -Pi

or I get no answer as in Example 10:
Example 10: A Laplace PDE with one homogeneous and three non-homogeneous conditions:
pde__10 := diff(u(x, y), x, x)+diff(u(x, y), y, y) = 0;
                    /  2         \   /  2         \    
                    | d          |   | d          |    
         pde__10 := |---- u(x, y)| + |---- u(x, y)| = 0
                    |   2        |   |   2        |    
                    \ dx         /   \ dy         /    
iv__10 := u(0, y) = 0, u(Pi, y) = sinh(Pi)*cos(y), u(x, 0) = sin(x), u(x, Pi) = -sinh(x);
      iv__10 := u(0, y) = 0, u(Pi, y) = sinh(Pi) cos(y),

        u(x, 0) = sin(x), u(x, Pi) = -sinh(x)
pdsolve([pde__10, iv__10]);

There are also no answer as in Examle 10 in the Examples 15, 18, 19
Can you give me a hint,  what could be wrong?
With kind regards
Wolfgang Gellien

 

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