This article, considering that grinding efficiency improvement of cement grinders can lead to production improvement per grinder, and starting with improving the fineness of finished products, has listed several measures to improve the production and quality of cement grinders.

Through a mixture of several grinding agents most in use and theagent of LQ 2301 compound can effectively increase the cement powders grinding efficiency and economicresults.

According to four big harbors actual cargo handling capacities, it obtains the marginal efficiency values and sorting of three big ca.

Consumption demand depends on consumption tendency while effective demand on capital marginal efficiency and interest rate.

The existence and development of finance can increase the net revenue of firm by increasing firm s financing amount and marginal efficiency of capital,and reducing firm s financing cost.

The paper analyzes the condition,possible areas and evolutional mechanism of economic crises through Keynes\' theory about marginal efficiency of capital,and makes an empirical study on mortgage crisis.

This paper computes the marginal effective tax rate(METR) of machine and building investment of the Chinese firms based on the method of King and Fullerton(1984),the research result shows that the METR of machine is higher than that of building.