(t) uc(t) 0U< U0 0 <U0 p (t) Uo-U uch (t) uci(t) uc(t=uch(t+uCp(t) uc(t=uCi(t)+uCs(t)t uC(t) U0 US US <U0 uCzi(t) uCzS(t) t uC(t) U0 US US <U0 uCp(t) uCh(t) U0 -US uC(t)=uCh(t)+uCp(t) uC(t)=uCzi(t)+uCzs(t)