The convector pits are covered with convrete grids that are prefabricated for building pigsties.

供热器并被通常用在猪圈上混凝土格栅覆盖。

Model testing study is made on prefabricated spiral V-notch blasting, and hydromatic method is used to simulate the quasi-static process in blasting of explosive.

因此，研究螺旋切槽裂纹扩展以及与螺旋角等关系，具有重要意义。