The compressibility of upper heavier fluid is a stable factor, while the compressibility of lower lighter fluid is an instable factor.

上层重流体的可压缩性是稳定因素，而下层轻流体的可压缩性是失稳因素。

youdao

The second-order shear of the basic flow represents an instable factor for the symmetric disturbance, and drives the unstable mesoscale disturbance to travel in the meridional direction;

基流二次切变对于中尺度对称扰动来说是一个不稳定因子，并且驱动不稳定的中尺度对称扰动在南北方向传播；

youdao

Operative methods include cervical disk excision, cervical inter-body fusion and bone grafting and inner fixation, instable factor elimination. But eligible condition is relatively short.

手术治疗的方法主要是颈椎间盘摘除，融合植骨内固定，消除失稳因素，但其适应证相对较窄。

youdao