2014年6月英语四级作文真题附范文(第2套):A Beautiful City in China

高级词汇使用较丰富，拼写做的很棒；采用了简单的衔接手法，行文流畅；适当增加一些从句的使用，会为文章添彩。

As Fig. 4 exhibits, a sharp increase between the relative pressures of 0.3 and 0.4 can be observed in the N2 adsorption isotherms of all samples. In addition, the hysteresis loop correlated with the capillary condensation of N2 inside the pore system can also be observed once the relative pressure above 0.4. The results confirm that all samples exhibit typical IV isotherms and mesoporous structure [33]. However, the relative pressures related to the sharp increase shift to lower values and the hysteresis loops become smaller in the isotherms of Fe3O4@MCM-41 and Cu(acac)2/n-Bu4NBr/Fe3O4@MCM-41 compared with those observed in the isotherm of MCM-41, indicating the pore size shifts to micropore possibly due to the introduction of Fe3O4 and active species inside the framework of MCM-41 [34]. It is consistent with the XRD patterns given in Figs. 2 and 3.