In the context of that changing phase of history this paper further displays the essential history of the citizen s scientific literacy construction of our country since the founding of the People s Republic of China in 1949 , and explores this phase of history by stages.

It also clarified the basic historical facts behind China s decision to send troops.

After a qualitative analysis of these fault trees, the minimal path sets and the important degree sequence for each basic event were obtained, according to which results caused by basic events could be forecasted and basic measures for accident avoidance could be decided.

In system safety theory, the problem to realize the given value of system safety target by deciding the reliability of each basic event has not been well solved till now.

Fault tree model is the graphical expression of connection of basic events which result in system fault, and used in qualitative and quantitative analysis of system fault model.

According to a qualitative analysis of casing fault tree, and by taking casing failure as the top event, 47 different essential events are found out, and each event can be equaled to Boolean equation.

This essay goes into details on how to determine the probability of a complex event if it consists of two or three basic events.

The paper will discuss the approachto analyzing importance of basic events by considering the probability of every failure and its extent of probable inju-ry,which is applied to safety analysis of deep tunnel co.

With pairing problems in classical probability as the example and through the forms of several solutions to one problem,the calculating formulas for basic events are presented.