伴随着大数据时代的来临,管理和利用大数据可以促进教学改革.在教学内容方面改革主要考虑兼顾开放性、普遍性与个性,注重交叉性与综合性,提倡案例教学和实践教学.在教学方法上重新解释适用于数学类基础课的"考一考、说一说、讲一讲、做一做、想一想"五步法.在考核评价方面提倡"重过程、轻结果"的考核方法,对于其中存在的问题做了详细阐述.

The concentration and profiles of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the environmental air, soil and plant samples around a hospital solid waste incinerator (HSWI) in Northwest of China were determined by HRGC/HRMS, and the flue gas samples of the HSWI were also involved. The results showed that the average concentration (I-TEQ) of PCDD/Fs in the exhaust gas was 184 ng x m(-3), which seriously exceeds the emission standard (0.5 ng x m(-3)). And the average concentration of PCDD/ Fs was 7.30 pg x m(-3) in the ambient air samples, 52.5 pg x g(-1) in the soil samples, and 146 pg x g(-1) in the leaves samples. All of them were at quite high levels. The concentrations of PCDD/Fs in air samples of downwind were obviously higher than those of upwind. The concentration increased and then decreased with the increase of distance from the HSWI, and the highest concentration occurred at the distance of 700 m from the HSWI. The mass concentration (I-TEQ) proportional distributions of 2, 3, 7, 8 substitution toxic dioxins in downwind air and soil samples was similar to those in the exhaust gas samples. The analysis results of PCDD/Fs concentrations, profiles distributions and principal components all showed that the major source of PCDD/Fs in this area was from the HSWI flue gas emissions.

This paper depicts two important algorithms of decision trees-ID3 and C4.5 in detail.The main ideas of different algorithms of decision trees are similar.It is essential to choose the appropriate algorithm to settle the specific problem and obtain precise prediction.