1. The research quality of the paper is not high enough, because SCI journals require very high quality papers. If the quality is not high enough, it is likely to be rejected or requested to be modified.

2. The submitted papers do not meet the requirements of SCI publication, and the research direction needs to be readjusted or submitted to other journals.

3. The topic of the paper is not concerned, which leads to the delay in publishing the paper. This situation is usually caused by narrow research topics, ordinary research contents and simple research methods.

4. The language of the paper is unclear and needs to be revised, which greatly affects the progress of publication. The reasons are mostly due to the author's poor English level, nonstandard language expression and grammatical errors.