简介：Inthispaper,nonnegativesolutionsforthedegenerateellipticsystemsareconsidered.First,nonnegativesolutionsforscalarequationwithspatialdiscontinuitiesarestudied.Thenthemethoddevelopedforscalarequationisappliedtostudyellipticsystems.Atlast,theexistencecriteriaofnonnegativesolutionsofellipticsystemsaregiven.

简介：

简介：

简介：Abstract.OnthebasisofclassificationofgeographicalpropertiesarollingdevelopmentgoalprogrammingmodelisformulatedincorrespondencewiththeecopatterngroupinFour-LakeArea.Inthismodel,thecontrolofschistosomiasisandstrengthen-Lugofthedrainage-storagefunctionarebothregardedasecologicalmeasuresduringtheprocessofmulti-year(r0)ecologicaleconomicrollingdevelopmenttomaketheecoagrlculturalsysteminthisareaintoastablyoperating,ordered,andgoodcyclicsystemunderthesupportofsomecontrollablefactors.