Constraint _scon[1] is not convex quadratic since it is an equality constraint.
subject to Quantity {j in O, i in 1..Y}: 0<= a[j,i] <=u[j] ;
subject to Quality {i in 1..Y}: s[i]= (sum {j in O} ( a[j,i]* qual[j] )) / ( sum {j in O} (a[j,i])) ;
subject to Numberofmints {i in 1..Y} : sum {j in O} ( w[j,i]) <= 3;
subject to Closedforever {j in O,i in 1..Y,f in 1..Y : f>=i } : k[j,f] <= k[j,i] ;
subject to Con {j in O,i in 1..Y} : a[j,i] <=M* w[j,i] ;
subject to Cons {j in O,i in 1..Y} : w[j,i]<=M *k[j,i] ;
And the variables are :
var a {O,1..Y};
var k {O,1..Y} binary ;
var w {O,1..Y} binary ;