Various pollutants emitted by coal-fired boilers are one of the main culprits of fog and haze forming in recent years especially in the north of China. The paper analyzes the fuel-switching project for district heating and main pollutant reductions, emission reductions of atmospheric particulate matter are calculated by materials accounting method. The economic, environmental and social benefits are also calculated according to pollutant reductions. It is shown that clean energy can be used for district heating. The project provides the theoretical basis for coal fired to gas fired reforming for district heating in the north area and has a guiding role for the other areas of China.

This paper put forward a new security assessment method for solving the problem of airport security assessment. In this method, the computer simulation technology is used to establish airport's virtual model, the perspective projection method is applied to achieve simulation roaming, and the fault tree analysis is utilized to evaluate the virtual model's security. By modularizing the method described above, the Airport Security Simulation System is developed successfully basing on the UG platform. An example, at the end of the paper, is given to show the application of the system. The result shows that this system is rational and pragmatic in airport security and safety risk evaluation.