<正>什么是MOOC1.概念MOOC是今年教育领域最热的话题,MOOC,Massive Open Online Courses,大规模、开放、在线、课程四个要素缺一不可,构成了MOOC之所以在短时间内能够被采纳被推广的重要因素。Massive,大规模。在上课过程中,人数最多的课有190多个国家的十几万人同时在学,一个学生提出问题,15分钟内肯定有回答,这种没有时差的回应对学生是动机上的激励,这是教学中很重要的一个因素。另外,我们在校内向学生推广网络学习平台时最大的问题是学生缺乏积极性,不爱上论坛发帖子或回复帖子,在MOOC这种大规模的平台上,即使发帖的人比例不大,也足以覆盖观点的维度,这有助于教学目标的完成。
Wang S, Ma S, Zhang L, Wang S, Zhao D, Gao W. Multi layer based rate control algorithm for HEVC, in 2013 IEEE International Symposium on Circuits and Systems (ISCAS2013), Beijing, China, May 19-23, 2013.; 2013:41–44. 访问链接
For sustainable geologic CO2 sequestration (GCS), a better understanding of the effects of brine cation compositions on mica dissolution, surface morphological change, and secondary mineral precipitation under saline hydrothermal conditions is needed. Batch dissolution experiments were conducted with biotite under conditions relevant to GCS sites (55–95 °C and 102 atm CO2). One molar NaCl, 0.4 M MgCl2, or 0.4 M CaCl2 solutions were used to mimic different brine compositions, and deionized water was used for comparison. Faster ion exchange reactions (Na+–K+, Mg2+–K+, and Ca2+–K+) occurred in these salt solutions than in water (H+–K+). The ion exchange reactions affected bump, bulge, and crack formation on the biotite basal plane, as well as the release of biotite framework ions. In these salt solutions, numerous illite fibers precipitated after reaction for only 3 h at 95 °C. Interestingly, in slow illite precipitation processes, oriented aggregation of hexagonal nanoparticles forming the fibrous illite was observed. These results provide new information for understanding scCO2–brine–mica interactions in saline aquifers with different brine cation compositions, which can be useful for GCS as well as other subsurface projects.
Two polymers, r-PDI-diTh and i-PDI-diTh, were synthesized as acceptors applicable for solution-processed BHJ OSCs. By introducing a bulky, dove tailed side chain and thereby suppressing the p-p interactions between perylenediimide units in the backbones of acceptor polymers, more effective phase segregation of these acceptors with a donor polymer (P3HT) was realized. By employing the inverted device configuration to better match the vertical phase separation of donor-acceptor polymers produced by solution processing, undesirable polaron pair recombination was suppressed, and PCE up to 2.17% was achieved from the regio-regular acceptor r-PDI-diTh.