In view of this,based on analvsis of the svstem of soil and water conservation forest in detail,he concept of the effective cover rate for soil and water conservation forest is advanced as the cover rate when the amount of soil loss is equal to .

The effective cover rate is of an important macro control index of building soil and water conservation forest.

The formation principle of trajectories of the points on a planetary gear is introduced and the following aspests are described, including the working principle of the ball-stirring mill, the basic structure, the driving design and the selection of structural shapes of the planetary stirrer and the determination of its effective coverage rate.

Namely,the method and optimization works applied here greatly improve DFT quality and its test coverage.

With the increasing enhancement of chip indensity and progress of manufacture technology,new test methodologies and fault models need to be developed to meet the target of high test coverage and product yield.

This paper presents a method,which uses metaheuristic search techniques for test date generation,to improve test coverage for the part of low probability to be executed in the programme under test.