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\n Synopsis
		sfduffing1 < in.rsf > out.rsf restor=restor.rsf gamma=0.75 omega=1 kxi=1 x0=0 y0=0 pow1=1 pow2=3 phi=0. verb=n cosine=y

Duffing equation: x\'\'/(omega^2)+0.5 x\'/omega-x+x^3=gamma cos(omega t+phi)+kxi R(t)
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\n Parameters
		\n \n \n \n   bool cosine=y [y/n] \tif n need extenal input for periodic restoring force \n \n \n\n \n \n \n   float gamma=0.75 \tstrength of external force \n \n \n\n \n \n \n   float kxi=1 \tadjustment for input signal \n \n \n\n \n \n \n   float omega=1 \tangular frequence of external force \n \n \n\n \n \n \n   float phi=0. \tphase of cosine signal unit=pi \n \n \n\n \n \n \n   int pow1=1 \tpower of first non-linear restitution term \n \n \n\n \n \n \n   int pow2=3 \tpower of second non-linear restitution term \n \n \n\n \n \n \n   string restor= \tauxiliary input file name \n \n \n\n \n \n \n   bool verb=n [y/n] \tverbosity flag \n \n \n\n \n \n \n   float x0=0 \tinitial value of x0 \n \n \n\n \n \n \n   float y0=0 \tinitial value of y0 \n \n \n

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