科研成果 by Year: 1996

1995年8月9日至11日,以北京大学副校长闵维方教授为领队的中国高等教育代表团一行7人抵加拿大阿尔伯塔省埃蒙顿市参加了"中加21世纪高等教育发展研讨会"。会议由中国北京大学和加拿大阿尔伯塔大学联合举办。中加与会代表36人。阿尔伯塔省高等教育及职业发展部副部长林·丹肯女士和北京大学副校长闵维方教授为大会做了主题发言。大会的宗旨是讨论21世纪世界(特别是中国和加拿大)高等教育所面临的问题。与会者就教育的作用,高等教育的宏观和微观管理,高教资金的筹集和分配,非正规教学手段的发掘和运用,以及大学和企业的关系等问题进行了热烈而深入的探讨。

Observations of aerosol chemistry and microphysics were made at Chebogue Point, Nova Scotia, from August 16 to September 8, 1993 as part of the North Atlantic Regional Experiment (NAPE) intensive. Most of the aerosols were classified into two groups according to the geometric mean volume diameter (D-gv) of the particles which contributed the greatest volume (sub-0.5 mu m) The group-1 aerosols; representing 33% of the data, are characterized by D-gv of 0.18-0.19 mu m; the group-2 aerosols, representing 50% of the data, are characterized by D-gv of 0.20-0.22 mu m; and the remaining aerosols bear similarities to either groups 1 or 2 but lie outside the D-gv ranges. The differences between these aerosol groups are consistent with the addition of sulfate to the group-2 aerosols via recent processing through cloud. Factors supporting this possibility include the presence of low marine stratus upwind of the site only on days when the group-2 aerosol was observed, the higher D-gv for the group-2 aerosols consistent with the observed size threshold for activation in these clouds, and the association of non-sea-salt SO4= (nssSO(4)(=)) with larger particle sizes for the group-2 aerosols. In general, the masses of the most abundant inorganic and organic ions, nssSO(4)(=) and oxalate, were associated with the main volume of the sub-0.5-mu m particles. Cloud condensation nucleus (CCN) concentrations active at 0.4% supersaturation (CCN0.4) were highly correlated with the concentrations of particles >0.01 mu m and oxalate and moderately correlated with nssSO(4)(=). Concentrations of CCN active at 0.06% supersaturation (CCN0.6) correlate very well with the concentrations of particles >0.19 mu m diameter. In the case of the recently cloud-processed aerosols, for which nssSO(4)(=) is more strongly associated with particles >0.19 mu m, the CCN0.06 also correlate well with nssSO(4)(=) CCN spectra computed using the measured size distributions and aerosol chemistry agree well with the measured CCN.