subroutine rms2int(  inverse, dt, vrms, nt,  vint )
integer it, wide,    inverse,           nt
real	vmin,	              dt, vrms( nt), vint( nt)
temporary real                     sum( nt), vis ( nt)
if( inverse == 0) {
	do it= 1, nt 
		sum(it)= ((it-1)*dt) * amax1( vrms(it)**2, 1.5**2 )
	vis(1) = amin1( vrms(1) ** 2 , 1.5 ** 2 )
	do it= 2, nt
		vis(it) = ( sum(it) - sum(it-1) )/ dt
	wide= 2;  repeat {
		vmin = vis(1);  do it=1,nt { if( vis(it)<vmin)  vmin = vis(it) }
		if( vmin > 0 )   break
		call triangle( wide, 1, nt, vis, vis)		# smooth vis()
		wide = wide + 1
		if( wide >= nt/3) call erexit('negative velocity')
		}
	do it= 1, nt
		vint(it) = sqrt( vis(it))
	}
else {				do it= 1, nt
					vis(it) = vint(it) ** 2
	sum(1) = 0.;		do it= 2, nt
					sum(it) = sum(it-1) + vis(it) * dt
	vrms(1) = vint(1);	do it= 2, nt
					vrms(it) = sqrt( sum(it) / ((it-1)*dt) )
	}
return;	end