 $\mu_{{\alpha}_i^+}(E_0,V_0)<\mu_{{\alpha}_i^+}(E_0,V_0)$,      0.  $(E_0,V_0)$ and $(E_0,V_0)$ are both ${\alpha}_i$-semistable, with $\mu_{{\alpha}_i}(E_0,V_0)=\mu_{{\alpha}_i}(E_0,V_0)$,      0.  $\frac{k_0}{n_0}$ is a m