1.Introduction Carbon neutrality has emerged as a global goal due to its pivotal role in addressing the challenges of global climate change.Before the United Nations Climate Summit was held in November 2020,124 countr...1.Introduction Carbon neutrality has emerged as a global goal due to its pivotal role in addressing the challenges of global climate change.Before the United Nations Climate Summit was held in November 2020,124 countries promised to reach net-zero emissions[1].Solar energy is one of the important renewable energy sources that significantly curtail carbon emissions originating from fossil fuels.展开更多
Inter-city mobility is one of the most important issues in the UN Sustainable Development Goals,as it is essential to access the regional labour market,goods and services,and to constrain the spread of infectious dise...Inter-city mobility is one of the most important issues in the UN Sustainable Development Goals,as it is essential to access the regional labour market,goods and services,and to constrain the spread of infectious diseases.Although the gravity model has been proved to be an effective model to describe mobility among settlements,knowledge is still insufficient in regions where dozens of megacities interact closely and over 100 million people reside.In addition,the existing knowledge is limited to overall population mobility,while the difference in inter-city travel with different purposes is unexplored on such a large geographic scale.We revisited the gravity laws of inter-city mobility using the 2.12 billion trip chains recorded by 40.48 million mobile phone users’trajectories in the Jing-Jin-Ji Region,which contains China’s capital Beijing.Firstly,unlike previous studies,we found that non-commuting rather than commuting is the dominant type of inter-city mobility(89.3%).Noncommuting travellers have a travel distance 42.3%longer than commuting travellers.Secondly,we developed more accurate gravity models for the spatial distribution of inter-city commuting and non-commuting travel.We also found that inter-city mobility has a hierarchical structure,as the distribution of inter-city travel volume follows Zipf’s law.In particular,the hierarchy of non-commuting travel volume among the cities is more in line with an ideal Zipf distribution than commuting travel.Our findings contribute to new knowledge on basic inter-city mobility laws,and they have significant applications for regional policies on human mobility.展开更多
Three-dimensional hierarchical structure coral-like BaTiO3 nanoparticles have been self-assembled by a facile one step hydrothermal method. Cetyltrimethyl ammonium bromide(CTAB),Ba(OH)2·8H2O and tetrabutyl titana...Three-dimensional hierarchical structure coral-like BaTiO3 nanoparticles have been self-assembled by a facile one step hydrothermal method. Cetyltrimethyl ammonium bromide(CTAB),Ba(OH)2·8H2O and tetrabutyl titanate have been used as precursors. The prepared Ba TiO3 exhibits cubic perovskite phase at room temperature,and the coral-like architecture is a micro-nano hiberarchy consisted of dendrimer-like structure and trunk-like structure. By adjusting the hydrothermal duration and the precursor substances,a surfactant induced mechanism is proposed to understand the self-assembly process. UV-vis measurement demonstrates that the as-prepared Ba TiO3 nanoparticles exhibit dozens of times overwhelming absorptive character compared to the ordinary nanospheres at ultraviolet band,which is benefited from the coral-like porous framework. Moreover,halogen anions( F,Cl,Br,and I) have been chosen to adjust the coral-like Ba TiO3 physical properties. Results show the halogen doping produces distinct modulation effect on the grain size,UV-vis absorbance and photoluminescence properties of the materials. The coral-like BaTiO3 nanoparticle and its halogen modified ramifications offer significant opportunities to develop nano-laser devices,photon detectors,photocatalyst based on BaTiO3 perovskite materials.展开更多
45 P_(2)O_(5)-15 BaO-25 ZnO-15 B2O_(3)glasses doped with different concentrations(0 mol%,0.1 mol%,0.25 mol%,0.5 mol%,and 0.75 mol%)of Gd^(3+)were prepared by a melt-quenching method and treated to fabricate glass-cera...45 P_(2)O_(5)-15 BaO-25 ZnO-15 B2O_(3)glasses doped with different concentrations(0 mol%,0.1 mol%,0.25 mol%,0.5 mol%,and 0.75 mol%)of Gd^(3+)were prepared by a melt-quenching method and treated to fabricate glass-ceramics containing BaZn_(2)(PO_(4))_(2)crystals by controllable crystallization.The structural,optical,and dosimetric properties were investigated.FTIR spectra indicate that the glasses are composed of[PO_(4)],[BO_(3)],and[BO_(4)]basic structural units.The XRD pattern analysis indicates that the samples contain BaZn_(2)(PO_(4))_(2)crystals.In the photoluminesce nce(PL)spectra,two emission bands are observed at 307 and 313 nm due to the^(6)P_(5/2)→^(8)S_(7/2)and^(6)P_(7/2)→^(8)S_(7/2)transitions of Gd^(3+),respectively.The OSL dosimetric properties of glass-ceramics were studied further under beta radiation of90Sr.The optimal Gd^(3+)doping concentration of 0.5 mol%was determined.The fading of the OSL signal shows that the CW-OSL signal of Gd^(3+)-doped BaZn_(2)(PO_(4))_(2)glass-ceramics decays by about 58.95%within120 h,and the intensity remains stable thereafter.The thermoluminescence(TL)curve has three peaks at 164,240,and 344℃.Minimum detectable dose(MDD)of the 0.5 mol%Gd^(3+)-doped BaZn_(2)(PO_(4))_(2)glass-ceramics was calculated as 0.675 mGy.The samples also exhibit good signal reusability and a broad linear dose-response range(0.3-500 Gy).Results show the excellent dosimetric properties of Gd^(3+)-doped BaZn_(2)(PO_(4))_(2)glass-ceramics and their potential application in radiation dosimetry.展开更多
文摘1.Introduction Carbon neutrality has emerged as a global goal due to its pivotal role in addressing the challenges of global climate change.Before the United Nations Climate Summit was held in November 2020,124 countries promised to reach net-zero emissions[1].Solar energy is one of the important renewable energy sources that significantly curtail carbon emissions originating from fossil fuels.
基金supported by the National Natural Science Foundation of China(Grant Nos.41925003&42130402)the Beijing Municipal Social Science Foundation(Grant No.20JCB073)。
文摘Inter-city mobility is one of the most important issues in the UN Sustainable Development Goals,as it is essential to access the regional labour market,goods and services,and to constrain the spread of infectious diseases.Although the gravity model has been proved to be an effective model to describe mobility among settlements,knowledge is still insufficient in regions where dozens of megacities interact closely and over 100 million people reside.In addition,the existing knowledge is limited to overall population mobility,while the difference in inter-city travel with different purposes is unexplored on such a large geographic scale.We revisited the gravity laws of inter-city mobility using the 2.12 billion trip chains recorded by 40.48 million mobile phone users’trajectories in the Jing-Jin-Ji Region,which contains China’s capital Beijing.Firstly,unlike previous studies,we found that non-commuting rather than commuting is the dominant type of inter-city mobility(89.3%).Noncommuting travellers have a travel distance 42.3%longer than commuting travellers.Secondly,we developed more accurate gravity models for the spatial distribution of inter-city commuting and non-commuting travel.We also found that inter-city mobility has a hierarchical structure,as the distribution of inter-city travel volume follows Zipf’s law.In particular,the hierarchy of non-commuting travel volume among the cities is more in line with an ideal Zipf distribution than commuting travel.Our findings contribute to new knowledge on basic inter-city mobility laws,and they have significant applications for regional policies on human mobility.
基金the Support Plan for Overseas Students to Return to China for Entrepreneurship and Innovation(cx2020003)the Fundamental Research Funds for the Central Universities(2020CDJQY-A028 and 2020CDJ-LHZZ-074)the Natural Science Foundation of Chongqing(cstc2020jcyj-msxmX0629)。
基金financially supported by the One Hundred Talents Project Foundation Program (1029271301)the Western Light Talent Culture Project (Grant No.RCPY201206) of Chinese Academy of Sciences+1 种基金the National Natural Science Foundation of China (Grant Nos.41302029 and 41130746)the International Technology Cooperation Foundation of Autonomous Region (20136009)
文摘Three-dimensional hierarchical structure coral-like BaTiO3 nanoparticles have been self-assembled by a facile one step hydrothermal method. Cetyltrimethyl ammonium bromide(CTAB),Ba(OH)2·8H2O and tetrabutyl titanate have been used as precursors. The prepared Ba TiO3 exhibits cubic perovskite phase at room temperature,and the coral-like architecture is a micro-nano hiberarchy consisted of dendrimer-like structure and trunk-like structure. By adjusting the hydrothermal duration and the precursor substances,a surfactant induced mechanism is proposed to understand the self-assembly process. UV-vis measurement demonstrates that the as-prepared Ba TiO3 nanoparticles exhibit dozens of times overwhelming absorptive character compared to the ordinary nanospheres at ultraviolet band,which is benefited from the coral-like porous framework. Moreover,halogen anions( F,Cl,Br,and I) have been chosen to adjust the coral-like Ba TiO3 physical properties. Results show the halogen doping produces distinct modulation effect on the grain size,UV-vis absorbance and photoluminescence properties of the materials. The coral-like BaTiO3 nanoparticle and its halogen modified ramifications offer significant opportunities to develop nano-laser devices,photon detectors,photocatalyst based on BaTiO3 perovskite materials.
基金Project supported by the National Natural Science Foundation of China(11675260)。
文摘45 P_(2)O_(5)-15 BaO-25 ZnO-15 B2O_(3)glasses doped with different concentrations(0 mol%,0.1 mol%,0.25 mol%,0.5 mol%,and 0.75 mol%)of Gd^(3+)were prepared by a melt-quenching method and treated to fabricate glass-ceramics containing BaZn_(2)(PO_(4))_(2)crystals by controllable crystallization.The structural,optical,and dosimetric properties were investigated.FTIR spectra indicate that the glasses are composed of[PO_(4)],[BO_(3)],and[BO_(4)]basic structural units.The XRD pattern analysis indicates that the samples contain BaZn_(2)(PO_(4))_(2)crystals.In the photoluminesce nce(PL)spectra,two emission bands are observed at 307 and 313 nm due to the^(6)P_(5/2)→^(8)S_(7/2)and^(6)P_(7/2)→^(8)S_(7/2)transitions of Gd^(3+),respectively.The OSL dosimetric properties of glass-ceramics were studied further under beta radiation of90Sr.The optimal Gd^(3+)doping concentration of 0.5 mol%was determined.The fading of the OSL signal shows that the CW-OSL signal of Gd^(3+)-doped BaZn_(2)(PO_(4))_(2)glass-ceramics decays by about 58.95%within120 h,and the intensity remains stable thereafter.The thermoluminescence(TL)curve has three peaks at 164,240,and 344℃.Minimum detectable dose(MDD)of the 0.5 mol%Gd^(3+)-doped BaZn_(2)(PO_(4))_(2)glass-ceramics was calculated as 0.675 mGy.The samples also exhibit good signal reusability and a broad linear dose-response range(0.3-500 Gy).Results show the excellent dosimetric properties of Gd^(3+)-doped BaZn_(2)(PO_(4))_(2)glass-ceramics and their potential application in radiation dosimetry.