function J=Jacobi(ie,kesi,yita,Elements,Nodes)            


ENodes = Elements(ie,:);                 %获取单元结点 
xe = Nodes(ENodes(:),:);                 %获取结点坐标 
x1=xe(1,1);y1=xe(1,2); 
x2=xe(2,1);y2=xe(2,2); 
x3=xe(3,1);y3=xe(3,2); 
x4=xe(4,1);y4=xe(4,2); 
J=1/4*[-(1-yita),(1-yita),(1+yita),-(1+yita);-(1-kesi),-(1+kesi),(1+kesi),(1-kesi)]*[x1 y1;x2 y2;x3 y3;x4 y4];