Two self-dual codes with larger lengths over ℤ9

In this paper, we introduce new definitions of the Gray weight and the Gray map for linear codes over ℤ9 + uℤ9 with u2 = u. Some results on self-dual codes over this ring are investigated. Further, the structural properties of quadratic residue codes are also considered. Two self-dual codes with new parameters [22, 11, 5] and [24, 12, 9] over ℤ9 are obtained.

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