We　present　a　unified　semidefinite　programming　hierarchies　rounding　approximation　algorithm　for　a　class　of　maximum　graph　bisection　problems　with　improved　approximation　ratios.　Under　the　above　algorithmic　framework,　we　show　that　the　approximation　ratios　of　MAX-n/2-CUT,　MAX-n/2-DENSE-SUBGRAPH,　and　MAX-n/　2-VERTEX-COVER　are　equal　to　those　of　MAX-n/2-UNCUT,　MAX-n/2-DIRECTED-CUT,　and　MAX-n/2-DIRECTED-UNCUT,　respectively.