Ring polymer molecular dynamics(RPMD)calculations for the C(^(1)D)+H_(2)reaction are performed on the Zhang-Ma-Bian ab initio potential energy surfaces(PESs)recently constructed by our group,which are unique in very g...Ring polymer molecular dynamics(RPMD)calculations for the C(^(1)D)+H_(2)reaction are performed on the Zhang-Ma-Bian ab initio potential energy surfaces(PESs)recently constructed by our group,which are unique in very good descriptions of the regions around conical intersections and of van der Waals(vdW)interactions.The calculated reaction thermal rate coefficients are in very good agreement with the latest experimental results.The rate coefficients obtained from the ground˜a^(1)A′ZMB-a PES are much larger than those from the previous RKHS PES,which can be attributed to that the vdW saddles on our PESs have very different dynamical effects from the vdW wells on the previous PESs,indicating that the RPMD approach is able to include dynamical effects of the topological structures caused by vdW interactions.The importance of the excited˜b^(1)A′′ZMB-b PES and quantum effects in the title reaction is also underscored.展开更多
Since the 1950s, there have been several food crises with severe humanitarian, economic, political and market-related consequences. In the last decade, food crises occurred during 2007-2008 and again in 2010-2011. In ...Since the 1950s, there have been several food crises with severe humanitarian, economic, political and market-related consequences. In the last decade, food crises occurred during 2007-2008 and again in 2010-2011. In the paper, the main explanations for the food crises are discussed with a focus on the 2007-2008 food crisis, and the main causes are divided into temporary/random and structural/long term and are listed. Although there are a large number of factors, the size of reserves, speculation and bioenergy seem to be significant causes of the rapidly increasing food prices which were a major cause of the food crisis. The consequences of the food crisis in 2007-2008 in particular are discussed, and some major lessons learnt are listed. Also, the present market situation is assessed, the conclusion of which is that there does not seem to be an immediate risk of another food crisis occurring in the short term. However, international cereal reserves are still vulnerable and lower compared to the level in the 1990s.展开更多
China＇s environmental problems have become increasingly serious, which have caused great attention of the relevant departments of the state. Through the survey, we found that in most of the cities in our country, the...China＇s environmental problems have become increasingly serious, which have caused great attention of the relevant departments of the state. Through the survey, we found that in most of the cities in our country, the inhalable particulate matter PM10 is one of the main pollutants, especially in the capital of China -- Beijing, which is the arch-criminal cause of the air pollution. According to the quality control report released in Beijing City Environmental Protection Bureau, as can be learned, in recent years, Beijing＇s air quality goes from bad to worse, and in the overall atmospheric pollutants, the PM10 is up to above nine tenths. There are more reports saying that the air pollution levels in Beijing have been not suitable for the human habitation. With the increasing of the air pollution, the term PM2.5 is also more and more familiar to us. The air more intensified the pollution is, the greater the ratio of PM2.5 in PM10 is. In that case, it not only seriously affects the people＇s health, but also brings the huge economic losses. This paper is aimed to analyze the influence of PM2.5 on the economic situation of Beijing, and puts forward the concrete solutions.展开更多
基金supported by the National Natural Science Foundation of China(No.21773251 and No.21973098)the Youth Innovation Promotion Association CAS(No.2018045)the Beijing National Laboratory for Molecular Sciences。
文摘Ring polymer molecular dynamics(RPMD)calculations for the C(^(1)D)+H_(2)reaction are performed on the Zhang-Ma-Bian ab initio potential energy surfaces(PESs)recently constructed by our group,which are unique in very good descriptions of the regions around conical intersections and of van der Waals(vdW)interactions.The calculated reaction thermal rate coefficients are in very good agreement with the latest experimental results.The rate coefficients obtained from the ground˜a^(1)A′ZMB-a PES are much larger than those from the previous RKHS PES,which can be attributed to that the vdW saddles on our PESs have very different dynamical effects from the vdW wells on the previous PESs,indicating that the RPMD approach is able to include dynamical effects of the topological structures caused by vdW interactions.The importance of the excited˜b^(1)A′′ZMB-b PES and quantum effects in the title reaction is also underscored.
文摘Since the 1950s, there have been several food crises with severe humanitarian, economic, political and market-related consequences. In the last decade, food crises occurred during 2007-2008 and again in 2010-2011. In the paper, the main explanations for the food crises are discussed with a focus on the 2007-2008 food crisis, and the main causes are divided into temporary/random and structural/long term and are listed. Although there are a large number of factors, the size of reserves, speculation and bioenergy seem to be significant causes of the rapidly increasing food prices which were a major cause of the food crisis. The consequences of the food crisis in 2007-2008 in particular are discussed, and some major lessons learnt are listed. Also, the present market situation is assessed, the conclusion of which is that there does not seem to be an immediate risk of another food crisis occurring in the short term. However, international cereal reserves are still vulnerable and lower compared to the level in the 1990s.
文摘China＇s environmental problems have become increasingly serious, which have caused great attention of the relevant departments of the state. Through the survey, we found that in most of the cities in our country, the inhalable particulate matter PM10 is one of the main pollutants, especially in the capital of China -- Beijing, which is the arch-criminal cause of the air pollution. According to the quality control report released in Beijing City Environmental Protection Bureau, as can be learned, in recent years, Beijing＇s air quality goes from bad to worse, and in the overall atmospheric pollutants, the PM10 is up to above nine tenths. There are more reports saying that the air pollution levels in Beijing have been not suitable for the human habitation. With the increasing of the air pollution, the term PM2.5 is also more and more familiar to us. The air more intensified the pollution is, the greater the ratio of PM2.5 in PM10 is. In that case, it not only seriously affects the people＇s health, but also brings the huge economic losses. This paper is aimed to analyze the influence of PM2.5 on the economic situation of Beijing, and puts forward the concrete solutions.
