Optimizing polymorphous silicon back surface field of a-Si(n)/c-Si(p) heterojunction solar cells by simulation;

The market background for PCK to develop the UOE welded steel pipes is discussed, followed by a description of PCK's technological level exemplified by employing the UOE process to produce grade X70 pipes for the West-to-East gas transport pipeline, thus demonstrating the PCK's rising by development.

The "target tracing prospecting" method is favourable to collect two kinds of materials for two kinds of geochemical fields: background field and anomaly field in large-scale bedrock geochemical exploration.

Using background field method,derive the field equations for a flat Robertson-Walder background,and show that the scalar potential is a exponential function.