Based on the monitoring data of ambient air quality and meteorological observation data,the characteristics and meteorological influencing factors of air pollution in Luojiang District of Deyang City from 2018 to 2022...Based on the monitoring data of ambient air quality and meteorological observation data,the characteristics and meteorological influencing factors of air pollution in Luojiang District of Deyang City from 2018 to 2022 were analyzed.The results show that from 2018 to 2022,the main air pollutants affecting the air quality of Luojiang District of Deyang City were PM_(2.5) and PM_(10),and the primary pollutant on heavy pollution days was basically PM_(2.5).PM_(2.5) and PM_(10) pollution showed obvious seasonal differences,and PM_(2.5) concentration exceeded the limit mainly in spring and winter,among which it was the most serious in early spring,especially in January and February,followed by December.PM_(10) exceeding the standard had a high seasonal correlation with PM_(2.5) exceeding the standard,mainly in spring and winter,among which it was the most serious in winter,especially in December,followed by January.PM_(2.5) and PM_(10) pollution showed an overall weakening trend.PM_(2.5) and PM_(10) concentration were closely related to meteorological factors such as temperature,relative humidity,wind speed,precipitation and air pressure,and were mainly affected by rainfall.展开更多
Co_(3)Sn_(2)S_(2)has attracted a lot of attention for its multiple novel physical properties,including topological nontrivial surface states,anomalous Hall effect,and anomalous Nernst effect.Vacancies,which play impor...Co_(3)Sn_(2)S_(2)has attracted a lot of attention for its multiple novel physical properties,including topological nontrivial surface states,anomalous Hall effect,and anomalous Nernst effect.Vacancies,which play important roles in functional materials,have attracted increasing research attention.In this paper,by using density functional theory calculations,we first obtain band structures and magnetic moments of Co_(3)Sn_(2)S_(2)with exchange–correlation functionals at different levels.It is found that the generalized gradient approximation gives the positions of Weyl points consistent with experiments in bulk Co_(3)Sn_(2)S_(2).We then investigate the electronic structures of defects on surfaces with S and Sn terminations which have been observed in experiments.The results show that the single sulfur vacancy on the S-terminated surface introduces localized bond states inside the bandgap near the Fermi level.For di-and tri-sulfur vacancies,the localized defect states hybridize with neighboring ones,forming bonding states as well as anti-bonding states.The Sn vacancy on the Sn-terminated surface also introduces localized bond states,which are merged with the valence bands.These results provide a reference for future experimental investigations of vacancies in Co_(3)Sn_(2)S_(2).展开更多
While the Harris-Todaro model is a traditional approach used in researching the urban-rural dichotomy,it fails to explain families’goals to maximize their current utility in terms of intertemporal decision-making con...While the Harris-Todaro model is a traditional approach used in researching the urban-rural dichotomy,it fails to explain families’goals to maximize their current utility in terms of intertemporal decision-making con‐ditions.To fill this gap,in this paper,an urban-rural dichotomy model involving labor migration and educa‐tion is established,in which it is assumed that family utility derives from consumption and children’s educa‐tional achievement.The steady-state path derived through the Bellman equation suggests that increasing edu‐cational investment and family education intensity leads to a significant urban-rural difference in children’s educational achievement.Compared with the traditional Harris-Todaro model,the transversality condition is loosened in this model,while the unavailability of loans constrains migrant families.Four hypotheses are made and tested using an empirical study.An ordinary least squares regression was used in the analysis,but due to the endogeneity caused by missing variables,the instrumental variable method and two-stage least squares regression were used.The results demonstrate that the household registration system can explain 44.5%of the educational achievement difference,and the initial difference is inflated 4.73 times after nine years of compulsory education.This divergence could increase the differences caused by household registra‐tion status,resulting in larger income gaps and intergenerational heredity of identities.展开更多
According to the differences between operation and correlationship by both sides of the takeover in the market for corporate control, the takeover can be divided into three types--transverse takeover, longitudinal tak...According to the differences between operation and correlationship by both sides of the takeover in the market for corporate control, the takeover can be divided into three types--transverse takeover, longitudinal takeover and mixed takeover. Meanwhile, due to the activities of takeover taken by the companies in the different trade life circles adopting different takeover types, so their performances are different. Seeing about this relationship, you can effectively inspect the efficiency of the market for corporate control. Adopting298 stylebook data from the market for corporate control in China, and through empirical analyzing, it can see that because of the existing of the stock holding, the efficiency of the market for corporate control in China is not very high. The government tempts to adjust the industrial structure through merger and acquisition （M＆A）, but it urged the aim of state-owned economy forward strategic transfer difficult to come true. To solve the contradiction of ＂setting up of the stock holding＂ comes to no time to delay. ＇展开更多
Exploring the fundamental building block is essential for constructing functional materials with extended topological configurations.In the polymeric nitrogen system,no fundamental building blocks have been reported s...Exploring the fundamental building block is essential for constructing functional materials with extended topological configurations.In the polymeric nitrogen system,no fundamental building blocks have been reported so far.Here,we successfully synthesize the buckled 1-dimensional(1D)band-shaped and 2-dimensional(2D)layered polymeric nitrogen frameworks with N_(18)ring as a fundamental building block for the first time.Furthermore,the dimensions of the polymeric nitrogen frameworks can be regulated by pressure conditions.Bader charge analyses indicate that the charge transfer from the La atom to the low-order bonded nitrogen atom plays a crucial role in stabilizing these two lowdimensional polymeric frameworks.Both LaN_(16)and LaN_(8)are promising high-energy-density materials(HEDMs).This study reveals that the N_(18)ring can serve as a fundamental building block,analogous to the six-membered ring in carbon-based materials,enabling the construction of novel polymeric nitrogen materials with extended frameworks.展开更多
文摘Based on the monitoring data of ambient air quality and meteorological observation data,the characteristics and meteorological influencing factors of air pollution in Luojiang District of Deyang City from 2018 to 2022 were analyzed.The results show that from 2018 to 2022,the main air pollutants affecting the air quality of Luojiang District of Deyang City were PM_(2.5) and PM_(10),and the primary pollutant on heavy pollution days was basically PM_(2.5).PM_(2.5) and PM_(10) pollution showed obvious seasonal differences,and PM_(2.5) concentration exceeded the limit mainly in spring and winter,among which it was the most serious in early spring,especially in January and February,followed by December.PM_(10) exceeding the standard had a high seasonal correlation with PM_(2.5) exceeding the standard,mainly in spring and winter,among which it was the most serious in winter,especially in December,followed by January.PM_(2.5) and PM_(10) pollution showed an overall weakening trend.PM_(2.5) and PM_(10) concentration were closely related to meteorological factors such as temperature,relative humidity,wind speed,precipitation and air pressure,and were mainly affected by rainfall.
基金the National Key R&D Program of China(Grant Nos.2019YFA0308500 and 2018YFA0305800)the National Natural Science Foundation of China(Grant Nos.51922011 and 61888102)+1 种基金Strategic Priority Research Program of the Chinese Academy of Sciences(Grant Nos.XDB30000000 and XDB28000000)the Fundamental Research Funds for the Central Universities,China。
文摘Co_(3)Sn_(2)S_(2)has attracted a lot of attention for its multiple novel physical properties,including topological nontrivial surface states,anomalous Hall effect,and anomalous Nernst effect.Vacancies,which play important roles in functional materials,have attracted increasing research attention.In this paper,by using density functional theory calculations,we first obtain band structures and magnetic moments of Co_(3)Sn_(2)S_(2)with exchange–correlation functionals at different levels.It is found that the generalized gradient approximation gives the positions of Weyl points consistent with experiments in bulk Co_(3)Sn_(2)S_(2).We then investigate the electronic structures of defects on surfaces with S and Sn terminations which have been observed in experiments.The results show that the single sulfur vacancy on the S-terminated surface introduces localized bond states inside the bandgap near the Fermi level.For di-and tri-sulfur vacancies,the localized defect states hybridize with neighboring ones,forming bonding states as well as anti-bonding states.The Sn vacancy on the Sn-terminated surface also introduces localized bond states,which are merged with the valence bands.These results provide a reference for future experimental investigations of vacancies in Co_(3)Sn_(2)S_(2).
文摘While the Harris-Todaro model is a traditional approach used in researching the urban-rural dichotomy,it fails to explain families’goals to maximize their current utility in terms of intertemporal decision-making con‐ditions.To fill this gap,in this paper,an urban-rural dichotomy model involving labor migration and educa‐tion is established,in which it is assumed that family utility derives from consumption and children’s educa‐tional achievement.The steady-state path derived through the Bellman equation suggests that increasing edu‐cational investment and family education intensity leads to a significant urban-rural difference in children’s educational achievement.Compared with the traditional Harris-Todaro model,the transversality condition is loosened in this model,while the unavailability of loans constrains migrant families.Four hypotheses are made and tested using an empirical study.An ordinary least squares regression was used in the analysis,but due to the endogeneity caused by missing variables,the instrumental variable method and two-stage least squares regression were used.The results demonstrate that the household registration system can explain 44.5%of the educational achievement difference,and the initial difference is inflated 4.73 times after nine years of compulsory education.This divergence could increase the differences caused by household registra‐tion status,resulting in larger income gaps and intergenerational heredity of identities.
文摘According to the differences between operation and correlationship by both sides of the takeover in the market for corporate control, the takeover can be divided into three types--transverse takeover, longitudinal takeover and mixed takeover. Meanwhile, due to the activities of takeover taken by the companies in the different trade life circles adopting different takeover types, so their performances are different. Seeing about this relationship, you can effectively inspect the efficiency of the market for corporate control. Adopting298 stylebook data from the market for corporate control in China, and through empirical analyzing, it can see that because of the existing of the stock holding, the efficiency of the market for corporate control in China is not very high. The government tempts to adjust the industrial structure through merger and acquisition （M＆A）, but it urged the aim of state-owned economy forward strategic transfer difficult to come true. To solve the contradiction of ＂setting up of the stock holding＂ comes to no time to delay. ＇
基金supported by the National Key R&D Program of China(2023YFA1406200)the National Natural Science Foundation of China(NSFC)(12174143,12404014)+1 种基金the Basic Science Center Project of NSFC(52388201)the China Postdoctoral Science Foundation funded project(2023M741352).
文摘Exploring the fundamental building block is essential for constructing functional materials with extended topological configurations.In the polymeric nitrogen system,no fundamental building blocks have been reported so far.Here,we successfully synthesize the buckled 1-dimensional(1D)band-shaped and 2-dimensional(2D)layered polymeric nitrogen frameworks with N_(18)ring as a fundamental building block for the first time.Furthermore,the dimensions of the polymeric nitrogen frameworks can be regulated by pressure conditions.Bader charge analyses indicate that the charge transfer from the La atom to the low-order bonded nitrogen atom plays a crucial role in stabilizing these two lowdimensional polymeric frameworks.Both LaN_(16)and LaN_(8)are promising high-energy-density materials(HEDMs).This study reveals that the N_(18)ring can serve as a fundamental building block,analogous to the six-membered ring in carbon-based materials,enabling the construction of novel polymeric nitrogen materials with extended frameworks.
