Patent Application Publication  Mar. 1, 2018 Sheet 7 of 18  US 2018/0055777 Al  FIG. 16  FIG. 17  8  ....  ..  7  ~  6  t  /  .  --0-with l>urfer  :  I  :=:  :a;  •\  ~  without buffer  ~  ~  \  .  :  t-----.~~--- 2  0  20  40  60  80  100  120 