visa for transit in Kunming and Shanghai

I am a Bangladeshi, studying PhD at Japan. 5th January 2013 I will go to Bangladesh and 5th February 2013 I will come back to Japan. I will travel through China Eastern Airlines. My flight details are:
on 5th January 2013, from Kansai, Osaka, Japan to Pudong, Shanghai, China. Transit time 2 hours and 40 minutes and no need to plane change. Than Pudong to Kunming, China and at Kunming 12 hours and 35 minutes transit time. Here I need to change the plane.
on 5th February 2013, from Dhaka, Bangladesh to Kunming, and at Kunming 13 hours and 5 minutes transit time. Here I need to change the plane. Than from Kunming to Pudong, China. Here transit time is 1 hour and 55 minutes but no need to change the plane.

My question is should I need any visa for China?