On the basis of analyzing the theories of fashion and raising the concept of the "center" and"margin"of fashion.

This paper discusses the mathematical backgrounds of the margin concept and elasticity notion in microeconomics and points out some applications in business management.

Many issues such as margin,flexibility,consumer surplus in economics relate to this important method——limit thinking.

Optimization of open-pit cutoff grade based on option pricing theory;

The determination of cutoff grade in mining operation is an important decision-making problem.

Brief talk about development of marginal oilfield in the western South China Sea;

Approach to key points in exploration and development of offshore marginal oilfields;

Application of horizontal well technology in the development of marginal oilfield in Bohai Bay;

Based on the analysis of current safety investment in China, safety investment theory of marginal utility is discussed, which is used to determine total amounu of safety investment.

Starting with the progressive decreasing theory of marginal utility in traditional economy,this paper points out that the network economy is marginal utility progressive increasing economy and discusses the reason for it.