Hi. After surrender the US Navy sent a special mission to evaluate several technical and statistical infos on the japanese naval power and naval and army research. They interrogated dozends of specialists, IJA and IJN officials and finally delivered over 180 reports on different topics. These reports contain very valuable informations on details about japanese technologies. They can be found at Reports of the U.S. Naval Technical Mission To Japan (1945 – 1946) It´s one of my primary sources and I can recommend reading them if you are interested in one or more of the topics. Yours tom!