The Yuan Friday traded at its highest level against the dollar since Beijing revalued the currency nearly a year ago, reports Wall Street Journal.   On Friday, the dollar closed at 7.9859 Yuan on the over-the-counter market, down from 7.9925 Yuan Thursday. It traded between 7.9850 and 7.9968 during the session. The dollar's level of 7.9850 Yuan was the lowest on the OTC market since the Yuan's revaluation.   Traders attributed the dollar's decline against the Yuan Friday in part to expectations the Chinese currency will appreciate in the long term. The dollar's weakness against major currencies in New York trading Thursday was likely also a factor.   Many foreign economists believe the Yuan is undervalued, and China's trading partners continue to call on Beijing to make its currency more flexible.