For its close relation to cryptography , coding theory and sequences , almost difference sets have attracted many scholars " attention . firstly , davis called a special kind of divisible difference set ( dds ) almost difference set . another kind of almost difference sets was defined by ding etc . for constructing binary sequence with three - level autocorrelation 最早, davis稱一類特殊的可分差集( dds )為幾乎差集,而后, ding等人為構(gòu)造具有優(yōu)的3級自相關(guān)函數(shù)的二元序列給出了幾乎差集的另一定義,并且利用分圓數(shù)構(gòu)造了很多類的幾乎差集。