For the past few years this has remained relatively constant—buoyed partly by the weak pound—but, as the chart shows, the trend over the decade to 2007 was slightly downward.
As the chart shows, the share of food samples that exceed the maximum residue limits (MRLs) in Europe has remained constant for many years.
如图表显示，食品抽检中，欧洲农残超标比例多年来一直居高不下。
3
Based on the basic equation of A. C. exciting alternator, the vector chart and power flow chart of the alternator are studied, and a method of variable-speed and constant frequency (VSCF) is proposed.