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Gas transmission compressor design.

Beightler, C., Phillips, D., Applied geometric programming. John Wiley
and Sons, New York, 1976.

Ali, M., Pant, M., Singh, V.P., Two modified differential evolution
algorithms and their applications to engineering design problems.
World Journal of Modeling and Simulation, vol.6, 2010, pp.72-80.
(Real life problem F1)
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Variables x1, x2, x3, obj;
Equations eobj;

eobj.. obj =e= 861000*(sqrt(x1))*x2*(x3**(-2/3))/sqrt(x2*x2-1)+
                36900*x3 +
                772000000*(x2**(0.219))/x1 -
                765430000/x1;

*Bound on variables:
x1.lo = 10;    x1.up = 55;
x2.lo = 1.1;   x2.up = 2;
x3.lo = 10;    x3.up = 40;

Model gtc /all/;

Solve gtc minimizing obj using nlp;

$ifThenI x%mode%==xbook
file gtcd /gtc1.dat/
put gtcd;
put x1.l:15:7, x2.l:15:7, x3.l:15:7 /;
put obj.l:15:7 /;
$endIf

* End gtc