Another underlying cause has been the drop in global spot prices and freight rates, which has driven many domestic miners of lower grade ore out of business.
另一个根本原因是全球铁矿石现价和海运费的降低，导致很多国内出产低品质铁矿石的矿厂歇业。
2
An attempt was made to define the safety grade of flanged connections according to target leakage rates described in domestic gasket standards and tightness rates of joints stated in PVRC of ASME.
The phosphor yield of domestic feed grade calcium monophosphate production processes is low, and there are a few production plants using the phosphoric acid concentration defluorination method.