First-principles calculations have been performed to investigate energetics and site preference of carbon (C) in a tungsten (W) 5(310)/[001] grain boundary (GB). We calculate the solution energies of the C atom in the...First-principles calculations have been performed to investigate energetics and site preference of carbon (C) in a tungsten (W) 5(310)/[001] grain boundary (GB). We calculate the solution energies of the C atom in the GB, which show that the interstitial C is energetically favored over the substitutional C. The segregation energy is calculated to be 3.95 eV for the energetically favorable GB interstitial site, indicating that C energetically prefers to segregate into the W GB. Based on the Rice-Wang model, our total energy calculations show that C has a significant beneficial effect on the W GB cohesion.展开更多
On the basis of the findings of 227 surveys of Chinese fertility intentions over the years 1980-2011, this paper investigates the longitudinal changes in fertility intentions through cross-temporal meta-analysis. It i...On the basis of the findings of 227 surveys of Chinese fertility intentions over the years 1980-2011, this paper investigates the longitudinal changes in fertility intentions through cross-temporal meta-analysis. It is found that the ideal number of children for the Chinese trended downwards from 1980, but since 2000 the average number has remained basically stable at 1.6 to 1.8. In the 1980s, people＇s fertility levels were higher than their fertility intentions. With economic and educational progress in China, both fertility levels and fertility intentions showed a downward trend, with the former declining faster than the latter. Since 1990, people＇s fertility levels have been lower than their fertility intentions; that is, their actual number of children has been less than their ideal number. This provides an empirical basis for examining the changes in China＇s fertility intentions and fertility levels.展开更多
基金supported by the National Magnetic Confinement Fusion Program (Grant No.2009GB106003)the National Natural Science Foundation of China (Grant No.50871009)support of the Innovation Foundation of BUAA for PhD Graduates
文摘First-principles calculations have been performed to investigate energetics and site preference of carbon (C) in a tungsten (W) 5(310)/[001] grain boundary (GB). We calculate the solution energies of the C atom in the GB, which show that the interstitial C is energetically favored over the substitutional C. The segregation energy is calculated to be 3.95 eV for the energetically favorable GB interstitial site, indicating that C energetically prefers to segregate into the W GB. Based on the Rice-Wang model, our total energy calculations show that C has a significant beneficial effect on the W GB cohesion.
基金supported by the Social Research and Database Construction Project of CentralUniversity of Finance and Economicsthe National Social Sciences Fund(Project No.:14CRK011)
文摘On the basis of the findings of 227 surveys of Chinese fertility intentions over the years 1980-2011, this paper investigates the longitudinal changes in fertility intentions through cross-temporal meta-analysis. It is found that the ideal number of children for the Chinese trended downwards from 1980, but since 2000 the average number has remained basically stable at 1.6 to 1.8. In the 1980s, people＇s fertility levels were higher than their fertility intentions. With economic and educational progress in China, both fertility levels and fertility intentions showed a downward trend, with the former declining faster than the latter. Since 1990, people＇s fertility levels have been lower than their fertility intentions; that is, their actual number of children has been less than their ideal number. This provides an empirical basis for examining the changes in China＇s fertility intentions and fertility levels.
