“…This kind of model is often referred to as Hidden Semi-Markov Model (HSMM; [8,9]). The commonly used duration distributions are Gamma [6,10,11], Gaussian [11], Poisson [5,8], and the uniform distribution [12], or alternatively, it can be simulated by combining some functions of the exponential function family [13]. Besides, expanded state HMM (ESHMM; [10,14]) models are also employed by some researchers to enhance the duration modeling capability of HMMs.…”