text: firstly,I consider you have to know the reason for your un-concentration. ( sleepy or not interest in the content .....)\nsecondly, you can find ways to solve them according to the reasons.\nit is simple for a sleepy student. but it is rather difficult to solve others . here i'd like to enjoy my experience on other problems, that is to set a goal for you in a period of time, thus you follow it actively.it is very useful.