Early research on the subject includes the work by Takuma [l], Bortnik and Vertikov [2], and Farish [3] and coworkers. Later, two joint research efforts were started independently by the Franco-British Gas Dis-charge Group [4] [5] and by an international research group sponsored by the Canadian Energy Association with participation of the BBC Research Center, the Technical University of Munich, CSIRO (Australia), the ETH Zurich, the University of Padova, and the Ontario Hydro Research Center. The results of this activity were presented in a joint publication [6].