In order to obtain liquefied products with higher yields of aromatic molecules to produce mesophase pitch,a good understanding of the relevant reaction mechanisms is required.Reactive molecular dynamics simulations we...In order to obtain liquefied products with higher yields of aromatic molecules to produce mesophase pitch,a good understanding of the relevant reaction mechanisms is required.Reactive molecular dynamics simulations were used to study the thermal reactions of pyrene,1-methylpyrene,7,8,9,10-tetrahydrobenzopyrene,and mixtures of pyrene with 1-octene,cyclohexene,or styrene.The reactant conversion rates,reaction rates,and product distributions were calculated and compared,and the mechanisms were analyzed and discussed.The results demonstrated that methyl and naphthenic structures in aromatics might improve the conversion rates of reactants in hydrogen transfer processes,but their steric hindrances prohibited the generation of high polymers.The naphthenic structures could generate more free radicals and presented a more obvious inhibition effect on the condensation of polymers compared with the methyl side chains.It was discovered that when different olefins were mixed with pyrene,1-octene primarily underwent pyrolysis reactions,whereas cyclohexene mainly underwent hydrogen transfer reactions with pyrene and styrene,mostly producing superconjugated biradicals through condensation reactions with pyrene.In the mixture systems,the olefins scattered aromatic molecules,hindering the formation of pyrene trimers and higher polymers.According to the reactive molecular dynamics simulations,styrene may enhance the yield of dimer and enable the controlled polycondensation of pyrene.展开更多
The core of"Long Forest"belief of the Dai nationality is to protect natural forests and forests for conservation of water supply as the home of ancestral gods of the nation and to maintain the ecological bal...The core of"Long Forest"belief of the Dai nationality is to protect natural forests and forests for conservation of water supply as the home of ancestral gods of the nation and to maintain the ecological balance by means of"Long Forest"worship,"Long Forest"taboo,the traditional customary law,and village regulation and non-governmental agreement.This paper takes Manjingchengzi Village in Xishuangbanna as an example to analyze the distribution of forest land in different periods over the past 60 years and explore the role of"Long Forest"belief in the conservation of local forest resources in a view to providing a frame of reference for regional ecological environment protection.展开更多
Fumin County is a satellite town closest to Kunming City,its economic development level has lagged behind that of the city and other districts and counties of the city,and the urbanization rate has been quite low.Thro...Fumin County is a satellite town closest to Kunming City,its economic development level has lagged behind that of the city and other districts and counties of the city,and the urbanization rate has been quite low.Through analyzing development conditions and problems of Fumin County,strategies and countermeasures were put forward for the new urbanization of the county during the Fourteenth Five-year Plan.展开更多
近年来,药物和个人护理品(Pharmaceuticals and Personal Care Products,PPCPs)在饮用水、污水及自然水体中被频繁检出,对生态及人类健康有潜在的不利影响。污水处理厂是PPCPs进入环境的主要途径之一,研究PPCPs在污水处理厂中的赋存与...近年来,药物和个人护理品(Pharmaceuticals and Personal Care Products,PPCPs)在饮用水、污水及自然水体中被频繁检出,对生态及人类健康有潜在的不利影响。污水处理厂是PPCPs进入环境的主要途径之一,研究PPCPs在污水处理厂中的赋存与去除具有重要意义。使用高效液相色谱-串联质谱联用仪(LC-MS/MS)分析了武汉市5个不同工艺污水处理厂中14种PPCPs的浓度和去除效率。结果表明:各污水处理厂进水中共检出13种PPCPs,总浓度范围为1 471~2 077 ng/L;污水处理厂对大部分目标污染物的总去除效率达到80%以上,在生物处理工艺阶段污染物的去除效率最好,去除机制主要是污泥的吸附和微生物的降解;各污水处理厂进水中PPCPs的质量负荷范围较高(>103.0 g/d),出水中PPCPs的排放量明显降低(<36.3 g/d)。展开更多
基金financially supported by the National Natural Science Foundation of China(Approval No.42172168).
文摘In order to obtain liquefied products with higher yields of aromatic molecules to produce mesophase pitch,a good understanding of the relevant reaction mechanisms is required.Reactive molecular dynamics simulations were used to study the thermal reactions of pyrene,1-methylpyrene,7,8,9,10-tetrahydrobenzopyrene,and mixtures of pyrene with 1-octene,cyclohexene,or styrene.The reactant conversion rates,reaction rates,and product distributions were calculated and compared,and the mechanisms were analyzed and discussed.The results demonstrated that methyl and naphthenic structures in aromatics might improve the conversion rates of reactants in hydrogen transfer processes,but their steric hindrances prohibited the generation of high polymers.The naphthenic structures could generate more free radicals and presented a more obvious inhibition effect on the condensation of polymers compared with the methyl side chains.It was discovered that when different olefins were mixed with pyrene,1-octene primarily underwent pyrolysis reactions,whereas cyclohexene mainly underwent hydrogen transfer reactions with pyrene and styrene,mostly producing superconjugated biradicals through condensation reactions with pyrene.In the mixture systems,the olefins scattered aromatic molecules,hindering the formation of pyrene trimers and higher polymers.According to the reactive molecular dynamics simulations,styrene may enhance the yield of dimer and enable the controlled polycondensation of pyrene.
文摘The core of"Long Forest"belief of the Dai nationality is to protect natural forests and forests for conservation of water supply as the home of ancestral gods of the nation and to maintain the ecological balance by means of"Long Forest"worship,"Long Forest"taboo,the traditional customary law,and village regulation and non-governmental agreement.This paper takes Manjingchengzi Village in Xishuangbanna as an example to analyze the distribution of forest land in different periods over the past 60 years and explore the role of"Long Forest"belief in the conservation of local forest resources in a view to providing a frame of reference for regional ecological environment protection.
基金Supported by Scientific Research Fund Project of Education Department of Yunan Province(2022J0483)。
文摘Fumin County is a satellite town closest to Kunming City,its economic development level has lagged behind that of the city and other districts and counties of the city,and the urbanization rate has been quite low.Through analyzing development conditions and problems of Fumin County,strategies and countermeasures were put forward for the new urbanization of the county during the Fourteenth Five-year Plan.
文摘近年来,药物和个人护理品(Pharmaceuticals and Personal Care Products,PPCPs)在饮用水、污水及自然水体中被频繁检出,对生态及人类健康有潜在的不利影响。污水处理厂是PPCPs进入环境的主要途径之一,研究PPCPs在污水处理厂中的赋存与去除具有重要意义。使用高效液相色谱-串联质谱联用仪(LC-MS/MS)分析了武汉市5个不同工艺污水处理厂中14种PPCPs的浓度和去除效率。结果表明:各污水处理厂进水中共检出13种PPCPs,总浓度范围为1 471~2 077 ng/L;污水处理厂对大部分目标污染物的总去除效率达到80%以上,在生物处理工艺阶段污染物的去除效率最好,去除机制主要是污泥的吸附和微生物的降解;各污水处理厂进水中PPCPs的质量负荷范围较高(>103.0 g/d),出水中PPCPs的排放量明显降低(<36.3 g/d)。
