We can explain this difference via the distinction between these two kinds of methods for performance improvement.
to get more complex features, we adopt a nonlinear transformation: where x t is the word representation of the t-th word, W 1 ∈ R n 1 ×n 0 , n 0 is the length of word representation, f is an activation function and we use tanh in our experiments, N is the number of words to be labeled in the sequence.