超谐波 meaning in English

ultra harmonics
ultraharmonics

Using this method not only the necessary condition of existence and the approximate analytic expressions of the periodic solutions for primary - harmonic , super - harmonic and sub - harmonic resonances can be obtained , but the criteria of stability for these solutions can also be gained
该方法给出了二阶强非线性非自治系统主谐波共振和超谐波、次谐波共振周期解存在的必要条件，求得了这些周期解的近似解析表达式，并且得出了解的稳定性判据。