Ultra- low temperature air is generated by the UCAG applying the Vortex Tube Theory.
After entering into the UCAG , compressed-air goes through several nozzles which are designed to force the air to spin. The air , being transformed into spinning air , undergoes separation into cold air and hot air , and the cold air moves to the cold end of the UCAG.
After writing The Hobbit, to whom did J.R.R. Tolkien lend the book?.