“…In practice, the computation of K, ; ' K,, instead of the explicit inverse Ks;' is performed, and this may be accomplished by any equation solver which takes advantages of the sparsity of Kss. When substituting equation (7) into equation (3), one notes that even K, ; M,, K, ; ' is not required explicitly but rather (K,: ' K,m)T M,, K, ; ' Ksm. Therefore, the expansion of equation (7) does not introduce a large amount of computation because Ksi' K,,, and @ are needed anyway.…”