why results become zero?

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Author Message   shi liang (caleb_shi) Member Username: caleb_shi Post Number: 7 Registered: 12-2004 Posted on Thursday, January 13, 2005 - 03:23 am:    Hi, Sir. Thanks so much for your help. According to your suggestion, i use a constant to replace lambda and changed the eigenvalue equations to direct PDE system. but the results i got are all zero. what is the reason of that? two particles in box test_all.pde (0.9 k)   Robert G. Nelson (rgnelson) Moderator Username: rgnelson Post Number: 305 Registered: 06-2003 Posted on Tuesday, January 18, 2005 - 04:14 pm:    I forgot to mention that since the boundary conditions for an eigenvalue problem are all zero, in order to run a direct solution you need to provide some form of excitation source at the desired frequency. See for example "Backstrom_Books | Deformation_and_Vibration | Elasticity | vib44.pde"   shi liang (caleb_shi) Member Username: caleb_shi Post Number: 8 Registered: 12-2004 Posted on Sunday, January 23, 2005 - 03:26 am:    Hi, Sir. What do u mean by "some form of excitation source at the desired frequency"? i read the example, but i did not understand it and dont know which part is about the "excitation source".