sfduffing2 (2.0-git)
2D/3D Velocity analysis by using Duffing differential equation solved by 4th order Runge-Kutta method.

        sfduffing2 < cmp.rsf > outf.rsf restor=restor.rsf winsz=200 v0=1000 dv=20 vn=100 t0=o1 deltat0=dt t0n=n1 gamma=0.75 omega=1 kxi=1 x0=0 y0=0 pow1=1 pow2=3 phi=0. cosine=y delta=0.01 verb=n gx=2.0
Duffing equation: x''/(omega^2)+0.5 x'/omega-x+x^3=gamma cos(omega t+phi)+kxi R(t)

bool cosine=y [y/n]
if n need extenal input for periodic restoring force
float delta=0.01
The density of judgement grid
float deltat0=dt
step lenth for t0 scan
float dv=20
step lenth for velocity scan
float gamma=0.75
strength of external force
float gx=2.0
Size of grid
float kxi=1
adjustment for input signal
float omega=1
angular frequence of external force
float phi=0.
phase of cosine signal unit=pi
int pow1=1
power of first non-linear restitution term
int pow2=3
power of second non-linear restitution term
string restor=
auxiliary input file name
float t0=o1
t0 scan start point
int t0n=n1
numbers of t0scan
float v0=1000
init Vel for velocity scan
bool verb=n [y/n]
verbosity flag
int vn=100
numbers of velscan
int winsz=200
for each trace,the width of window. Unit:samples
float x0=0
initial value of x0
float y0=0
initial value of y0