Hi,
excellent! Thank you very much!
Joa
Den onsdagen den 21:e maj 2014 kl. 17:12:51 UTC+2 skrev Dima Pasechnik:
>
> On 2014-05-21, st...@joa.me.uk <javascript:> <st...@joa.me.uk<javascript:>>
> wrote:
> > Hi,
> >
> > it is a system of resitors and capacitors. I can in principle do a bit
> of
> > math and calculate Ztotal of my circuit. And calculate Itotal. From this
> I
> > can get the current I want by repeated current splitting in parallel
> > impedances. I have tried this as well. The results are the same. The
> > problem is not the solution itself
> >
> > sage: Rin*S[0][i8].subs({Uut:1})
> > -I*Cplunger*R1*Rin*w/((I*(C*Rin + (Ccable3 +
> > Cin)*Rin)*Ccable2*Cplunger*R1*R2 + I*((C*Rin + (Ccable3 +
> > Cin)*Rin)*Ccable2*R2 + (C*Rin + (Ccable3 +
> > Cin)*Rin)*Cplunger*R2)*Ccable1*R1)*Rut*w^3 + (((C*Rin + (Ccable3 +
> > Cin)*Rin)*Ccable2*R2 + (C*Rin + (Ccable3 + Cin)*Rin)*Cplunger*R2)*R1 +
> > ((Ccable2*(R2 + Rin) + C*Rin + (Ccable3 + Cin)*Rin)*Cplunger*R1 + (C*Rin
> +
> > (Ccable3 + Cin)*Rin)*Cplunger*R2 + ((Ccable2*(R2 + Rin) + Cplunger*(R2 +
> > Rin) + C*Rin + (Ccable3 + Cin)*Rin)*R1 + (C*Rin + (Ccable3 +
> > Cin)*Rin)*R2)*Ccable1)*Rut)*w^2 + (-I*(Ccable2*(R2 + Rin) + Cplunger*(R2
> +
> > Rin) + C*Rin + (Ccable3 + Cin)*Rin)*R1 - I*(C*Rin + (Ccable3 +
> Cin)*Rin)*R2
> > + (-I*Ccable1*(R1 + R2 + Rin) - I*Cplunger*R1 - I*Cplunger*(R2 +
> > Rin))*Rut)*w - R1 - R2 - Rin)
> >
> > which is not so complicated as, as it should, the same independant of
> way
> > of getting it (btw, sage is supposed to do the hard work for me, no? ;)
>
> >
> >
> > sage: Rin*S[0][i8].subs({Uut:1}).real()
> >
> -(C*Ccable1*Ccable2*Cplunger*R1^2*R2*Rin*Rut*w^4/(C^2*Ccable1^2*Ccable2^2*R1^2*R2^2*Rin^2*Rut^2*w^6
>
>
> > + 2*C*Ccable1^2*Ccable2^2*Ccable3*R1^2*R2^2*Rin^2*Rut^2*w^6 +
> > Ccable1^2*Ccable2^2*Ccabl....
> >
> > which continues for some 65000 terms... and this does not seem to
> optimized
> > to me. So, can I simplify this or not? I go to sympy after this stage
> only
> > to creat the c code
>
> Yes, I think Sage (or, rather, it's probably Maxima which does the
> hard lifting behind the scene) that does not know a good way to do
> the real part of a rational function. You can help it as follows,
> by doing numerator and denominator separately:
>
> e=Rin*S[0][i8].subs({Uut:1})
>
> e_d=e.denominator()
> e_num=(e_d.conjugate()*e.numerator()).expand()
> e_denom=(e_d.conjugate()*e_d).expand()
> # now e==e_num/e_denom, with e_denom real
> # and the following are your real and complex parts
> # use simplify_rational() to cancel common factors
> e_real=(e_num.real()/e_denom).simplify_rational()
> e_imag=(e_num.imag()/e_denom).simplify_rational()
>
> # now your e_real and e_imag have just a hundred terms or so...
>
> HTH
> Dmitrii
>
>
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