VTLVZ -- Velocity as function of Time for Linear V(Z);		
          writes out a vector of velocity = v0 exp(a t/2)		

 vtlvz > velfile nt= dt= v0= a= 					

 Required parameters							
 nt=	number of time samples						
 dt=	time sampling interval						
 v0=	velocity at the surface						
 a=	velocity gradient