径距 meaning in English

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The dynamic model in the spherical coordinate is presented for bearing - only target positioning . however , such model has unknown covariance of process noise , which is related to the range between the target and the passive sensor
简要概述被动定向跟踪，推导了球坐标系下的匀速运动目标的定向跟踪模型；状态建模的不完备性引起了模型噪声方差阵带有未知径距参数，因而需要解决参数在线辨识问题。
The wind rates of roots blower with these various kinds of three - lobe circular arc rotor are calculated and comparison between their performances is carried out . it is found that three - lobe rotor with external - internal circular arc and cycloid can produce the largest air volume . comparing the air pulsation produced by cylinder rotor and helix rotor , and proof that the structure of helix rotor can reduce the noise of roots blower
本文给出了罗茨鼓风机三种不同的圆弧转子型线的参数方程(外圆弧及其包络线型、内圆弧及其包络线型、和内外圆弧加摆线型) ，还给出了这三种转子的径距比( r _ a a )的极值，并进行比较，得到：内外圆弧加摆线线型是最优线型这一结论；为降低罗茨风机的噪声，将传统的直叶转子改成扭叶转子。