“…As two important system structures in reliability theory and engineering, the parallel and series systems have been studied comprehensively, interested readers may refer to Boland et al [6], Singh and Misra [41], Hu and Wang [25], Da et al [11], Navarro and Spizzichino [38], Yan et al [47], Yan and Luo [45], Chen et al [7], Fang and Wang [20], Kundu et al [29], Yan and Wang [46], Majumder et al [36] and the reference therein. Some researchers also focus on the optimal allocation of components for -out-of- systems and the general coherent systems, refer to Bhattacharya and Samaniego [5], Li and Ding [32], Ding and Li [15], You et al [50], Zhang [51], Ding et al [16], Ling and Wei [34], Guo et al [23], Torrado [44] and Yan et al [49].…”