Dong Cheng Union College   807 Union Street Schenectady, NY 12308 USA   chengd@union.edu   https://sites.google.com/site/chengdongvanderbilt/           JEL Areas: N7 : Economic History: Transport, International and Domestic Trade, Energy, Technology, and Other Services: General, International, or Comparative O3 : Technological Change; Research and Development: General