Conclusions: MPCNL is a therapeutic modality with advantages of high achievement ratio and slight injury especially for upper ureteric calculus with narrow ureter and ureter twist.
With twist-against-twist composite yarn, the correlation between breaking strength, breaking elongation ratio and twistof single yarn, twist of composite yarn are analyzed.
In the spinning process equalization point of the yarn is influenced by twist, spinning tension, roving interval, and overfeed ratio. Certain relationship exists among them.