!Copyright (c) 2013 by tdem.org under guide of Xiu Li(lixiu@chd.edu.cn)
!written by Huaifeng Sun(sunhuaifeng@gmail.com) and Xushan Lu(luxushan@gmail.com)
!Code distribution @ tdem.org or sunhuaifeng.com
    
!梯形波电流激发，采用升余弦开关函数和降余弦开关函数
SUBROUTINE TIXING_SOURCE_UPCOS
  USE CONSTANTPARAMETERS
  USE ELECTROMAGNETIC_VARIABLES
  USE RES_MODEL_PARAMETER
  USE TIME_PARAMETER
  USE OMP_LIB
  IMPLICIT NONE
  REAL(KIND=8)T0
  integer i,j,k
  WAVESTEP=TIME_MAX             !Time_max is given in Time_series subroutine:  TIME_MAX=GridSize*SQRT(EPS0*MU0/3.0)
  T0=1.13*MU0*SIGMA_MIN*GridSize*GridSize
  CTIME(1)=0.0D0   !RAISESTEP  !RAISETIME/STEP  !1.13*MU0*DELX*DELX/RES(1,1,1)
  DELT(1)=RAISESTEP    !RAISETIME/STEP
  DELT(0)=DELT(1)
  SOURCE(1)=AMP*0.5*(1-COS(PI*CTIME(1)/RAISETIME))  !AMP*CTIME(1)/RAISETIME
  DO I=2,NSTOP
     CTIME(I)=CTIME(I-1)+DELT(I-1)
     IF(CTIME(I) .LT. RAISETIME)THEN
        DELT(I)=RAISESTEP
        SOURCE(I)=AMP*0.5*(1-COS(PI*CTIME(I)/RAISETIME))  !AMP*CTIME(I)/RAISETIME
     ELSEIF(CTIME(I) .GE. RAISETIME .AND. CTIME(I) .LT. RAISETIME+WAVE-TIME_RAMP2WAVE_SUM)THEN
        DELT(I)=DELT(I-1)*1.0005
        IF(DELT(I) .GE. WAVESTEP)THEN
           DELT(I)=WAVESTEP
        ENDIF
        SOURCE(I)=AMP  !1.0D0
     ELSEIF(CTIME(I) .GE. RAISETIME+WAVE-TIME_RAMP2WAVE_SUM .AND. CTIME(I) .LT. RAISETIME+WAVE)THEN
        DELT(I)=DELT(I-1)*0.9995
        IF(DELT(I) .LE. RAMPSTEP)THEN
           DELT(I)=RAMPSTEP
        ENDIF
        SOURCE(I)=AMP
     ELSEIF(CTIME(I) .GE. RAISETIME+WAVE .AND. CTIME(I) .LT. RAISETIME+WAVE+RAMP)THEN
        DELT(I)=RAMPSTEP
        SOURCE(I)=AMP-AMP*0.5*(1-COS(PI*(CTIME(I)-RAISETIME-WAVE)/RAMP))   !+AMP*(+RAMP)/RAMP  !-AMP*CTIME(I)/RAMP+AMP*(RAISETIME+WAVE+RAMP)/RAMP
     ELSEIF(CTIME(I) .LT. RAISETIME+WAVE+RAMP+T0)THEN
        DELT(I)=RAMPSTEP
        SOURCE(I)=0.0D0
     ELSE
        DELT(I)=0.1*GridSize*SQRT(MU0*SIGMA_MIN*(CTIME(I)-RAISETIME-WAVE-RAMP)/6.0D0) !This can be changed if the value of GridSize is less than 1m.
        SOURCE(I)=0.0D0
        IF(DELT(I) .GT. 2.0D-7)THEN
           DELT(I)=2.0D-7      !1.0D-9  !
        ELSEIF(DELT(I) .LT. RAMPSTEP)THEN
           DELT(I)=RAMPSTEP
        ENDIF
     ENDIF
  ENDDO
  RETURN
ENDSUBROUTINE TIXING_SOURCE_UPCOS