hi i am solving 3D heat diffusion equation could you tell me the process of boundary condition  application in the main problem. i want to use mixed boundary condition that is robin boundary condition. how the boundary condition will effect the system stiffness and the mass matrix? or plz tell me some good books' name  from where i can get some idea.

plz plz plz 

hi, how r u everybody?

 hi,

 i have calculated the local stiffness matrix and form global stiffness matrix. but when i am solving the equation  it is saying the matrix (stiffness) is badly scaled and near to singular matrix. i think there is one problem in assembling the local matrix. anybody can give  the idea  what will be the probabal solution. i have done the 2d and its working fine. i have some doubt on  assembling. what i have done is that i have use the same algorithm of 2d( linear basis is triangle) assemble but different degrees of freedom and ofcourse node number will be differents for 3D ( basia is linear tetrahedron).

plz help me  i am on my deadline