pdf文件内容提取。将pdf文件中的文字内容提取出来，并生成相应的txt文件。,pdf file content extraction. Pdf document will be the text content extracted, and generates the corresponding txt file.

changing infix notation to prefix notation when calculating

paralell trans 3 phase with matlab. Improving the efficiency of three-phase squirrel cage induction motors, which are the most energy consuming electric machines in the world, saves much energy. The efficiency can be raised by optimizing the in