简介:Aderivativepatchinterpolatingrecoverytechniqueisanalyzedforthefiniteelementapproximationtothesecondorderellipticboundaryvalueproblemsintwodimensionalcase.Itisshownthattheconvergencerateoftherecoveredgradientadmitssuperconvergenceontherecoveredsubdomain,andistwoorderhigherthantheoptimalglobalconvergencerate(ultracovergence)ataninternalnodepointwhenevenorderfiniteelementspacesandlocaluniformmeshesareused.