Chapter 2 presents the first quasi-simultaneous multi-frequency (2.3, 5.0, 8.4 and 15.4GHz) VLBI observations of the Compact Steep Spectrum (CSS) source 3C 138, and the fast-switching phase-reference observation was used only at 15.4GHz.是什么意思_Chapter 2 presents the first quasi-simultaneous multi-frequency (2.3, 5.0, 8.4 and 15.4GHz) VLBI observations of the Compact Steep Spectrum (CSS) source 3C 138, and the fast-switching phase-reference observation was used only at 15.4GHz.在线翻译_英语_读音_用法_例句