variable zone
5.It is recommended to develop simpler and practical variable width models,construct riparian buffer net along all the rivers in agricultural catchments,design multi -zone buffers as possib le as can and implement best manageme nt practices(BMPs )in buffers.
8.The main features of the system are as follows: (1) There is no direct mechanical connection between engine and wheel, so the engine can be adjusted to work at high efficiency zone. (2) The power of the engine can be transmitted to driving axle directly by the electromagnetic force, and only part of power is converted from mechanical energy into electric energy, so the power losses in energy conversion can be reduced. (3) The system can also operate as electronic continuously variable transmission.

