Construction of trapezoidal channel and u-channel at ch2130 .
于2130里程距离兴建梯形渠及u渠。
Unscrew the central bolt and set it down in such a way that the conical area or trapezoidal thread cannot get dirty .
拧下中心螺栓并将其妥善放置，避免弄脏锥形区域或梯形螺纹。
The purpose of this study is to find the optimal order quantity and discount policy for inventory problem when demands are trapezoidal fuzzy number and quantity discount policy was offered by suppliers .
