The‘Practice of International Trade’is a subject specialized in studying the international exchange of commodities, It is a comprehensive applied science with substantial content And this thesis analysis the practical significance of studying this subject as well as the learning methods, the focuses and difficultie

Research conclusions:Based on the difficulty points and characteristics of underground pipelines detection,the analyses of the influencing factors on the underground pipelines detection for railway are made,and the countermeasures and resolution to improving the detection quality of underground pipeline for railway are offered.