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
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
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
The human settlement system is central to land use,infrastructure development,and environmental impacts.Although central place theory(CPT)was proposed about 90 years ago and has been extensively examined by many resea...The human settlement system is central to land use,infrastructure development,and environmental impacts.Although central place theory(CPT)was proposed about 90 years ago and has been extensively examined by many researchers,to what extent CPT can explain the current rural settlement system in the changing age of informatization and geospatial reconstruction remains to be explored.This paper aims to contribute fresh evidence for settlement systems and examine the applicability of CPT's quantitative laws by using the trajectory data of 2.0362 billion trips from 37.53 million mobile phone users in China's Jing-Jin-Ji region(218,000 km2 area).We found that the settlement system's distribution patterns and service range conformed with the hierarchical law in CPT.However,the former was closer to the administrative principle(K=7)in Christaller's theory,while the latter was nearer to the marketing principle(K=3).The basic service range of all levels of settlements for rural residents was approximately 3 km,which was reflected by the rural residents'3 km travel volume peak point.When exceeding this distance,the relationship between travel volume and distance distribution changed from linear increase to power-law attenuation.The traditional three principles of CPT influenced the settlements’service range and K value.Nevertheless,the specific roles of the influencing factors varied in space.The findings of this paper would enhance our knowledge of CPT and settlement systems in the context of a fast growing and rapidly urbanizing society.展开更多
Land cover products provide critical information for monitoring and analyzing land surface changes.However,notable disagreement and incompatible classification systems among existing land cover products bring challeng...Land cover products provide critical information for monitoring and analyzing land surface changes.However,notable disagreement and incompatible classification systems among existing land cover products bring challenges in using them.Here,we developed a hierarchical International Geosphere-Biosphere Programme(IGBP)classification system and integrated four widely used land cover products(i.e.,MODIS-IGBP,ESA-CCI,GlobeLand30,and GLC_FCS30)based on their accuracy against a collection of global reference samples.We generated a hybrid global annual land cover product(HYBMAP)with~1 km(1/120°,30″)spatial resolution from 2000 to 2020.The HYBMAP integrates information from the four products of high-and medium-resolution and reduces the disagreement between them by up to 20.1%.The overall accuracy of the HYBMAP is 75.5%,which is higher than the best of the four products(MODIS-IGBP,70.9%).HYBMAP also integrates the temporal change information from the four products and identifies a faster growth of built-up lands.The HYBMAP provides more consistent and reliable global land cover time series data for global change research.It is free to access at https://doi.org/10.5281/zenodo.10488191.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
The deep-level traps at grain boundaries(GBs)and halide ion migration are quite challenging for further enhancement of the stability and efficiency of perovskite solar cells(PSCs)as well as for the elimination of noto...The deep-level traps at grain boundaries(GBs)and halide ion migration are quite challenging for further enhancement of the stability and efficiency of perovskite solar cells(PSCs)as well as for the elimination of notorious hysteresis.Herein,we report a large-sized strongly coordinated organic anion GB anchoring strategy for suppressing ion migration and passivating defects in planar PSCs.The practical implementation of this strategy involves the incorporation of potassium salts containing a large-sized organic counter anion(4-sulfobenzoic acid monopotassium salt,SAMS)into the perovskite precursor.It has been found that anions within SAMS can be firmly anchored at GBs due to the strong coordination interaction between C=O and/or S=O at both ends of bulky anion and undercoordinated Pb^(2+)and/or halide vacancies,along with the hydrogen bond between–OH and formamidinium.SAMS can not only passivate shallowlevel defects but also cause more effective passivation of the deep-level defects.The GB manipulation strategy results in a reduced defect density,an increased carrier lifetime as well as suppressed ion migration,which in turn contributed to enhanced efficiency and stability of PSCs together with a thorough elimination of hysteresis.As a result,the SAMSmodified device with an outstanding fill factor of 0.84 delivers a significant improvement in efficiency(22.7%)in comparison with the control device(20.3%).The unencapsulated modified device demonstrates only little degradation after 1320 h at 60℃.展开更多
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.
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.
基金supported by the National Natural Science Foundation of China(41925003&42130402)Shenzhen Science and Technology Program(JCYJ20220818100810024)Beijing Postdoctoral Research Foundation(2022-ZZ-102).
文摘The human settlement system is central to land use,infrastructure development,and environmental impacts.Although central place theory(CPT)was proposed about 90 years ago and has been extensively examined by many researchers,to what extent CPT can explain the current rural settlement system in the changing age of informatization and geospatial reconstruction remains to be explored.This paper aims to contribute fresh evidence for settlement systems and examine the applicability of CPT's quantitative laws by using the trajectory data of 2.0362 billion trips from 37.53 million mobile phone users in China's Jing-Jin-Ji region(218,000 km2 area).We found that the settlement system's distribution patterns and service range conformed with the hierarchical law in CPT.However,the former was closer to the administrative principle(K=7)in Christaller's theory,while the latter was nearer to the marketing principle(K=3).The basic service range of all levels of settlements for rural residents was approximately 3 km,which was reflected by the rural residents'3 km travel volume peak point.When exceeding this distance,the relationship between travel volume and distance distribution changed from linear increase to power-law attenuation.The traditional three principles of CPT influenced the settlements’service range and K value.Nevertheless,the specific roles of the influencing factors varied in space.The findings of this paper would enhance our knowledge of CPT and settlement systems in the context of a fast growing and rapidly urbanizing society.
基金supported by the National Natural Science Foundation of China(42271104)the Shenzhen Funda-mental Research Program(GXWD20201231165807007-20200814213435001)+1 种基金the Shenzhen Science and Tech nology Program(JCYJ20220531093201004)Shenzhen Science and Technology Program(KQTD20221101093604016).
文摘Land cover products provide critical information for monitoring and analyzing land surface changes.However,notable disagreement and incompatible classification systems among existing land cover products bring challenges in using them.Here,we developed a hierarchical International Geosphere-Biosphere Programme(IGBP)classification system and integrated four widely used land cover products(i.e.,MODIS-IGBP,ESA-CCI,GlobeLand30,and GLC_FCS30)based on their accuracy against a collection of global reference samples.We generated a hybrid global annual land cover product(HYBMAP)with~1 km(1/120°,30″)spatial resolution from 2000 to 2020.The HYBMAP integrates information from the four products of high-and medium-resolution and reduces the disagreement between them by up to 20.1%.The overall accuracy of the HYBMAP is 75.5%,which is higher than the best of the four products(MODIS-IGBP,70.9%).HYBMAP also integrates the temporal change information from the four products and identifies a faster growth of built-up lands.The HYBMAP provides more consistent and reliable global land cover time series data for global change research.It is free to access at https://doi.org/10.5281/zenodo.10488191.
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)。
文摘The deep-level traps at grain boundaries(GBs)and halide ion migration are quite challenging for further enhancement of the stability and efficiency of perovskite solar cells(PSCs)as well as for the elimination of notorious hysteresis.Herein,we report a large-sized strongly coordinated organic anion GB anchoring strategy for suppressing ion migration and passivating defects in planar PSCs.The practical implementation of this strategy involves the incorporation of potassium salts containing a large-sized organic counter anion(4-sulfobenzoic acid monopotassium salt,SAMS)into the perovskite precursor.It has been found that anions within SAMS can be firmly anchored at GBs due to the strong coordination interaction between C=O and/or S=O at both ends of bulky anion and undercoordinated Pb^(2+)and/or halide vacancies,along with the hydrogen bond between–OH and formamidinium.SAMS can not only passivate shallowlevel defects but also cause more effective passivation of the deep-level defects.The GB manipulation strategy results in a reduced defect density,an increased carrier lifetime as well as suppressed ion migration,which in turn contributed to enhanced efficiency and stability of PSCs together with a thorough elimination of hysteresis.As a result,the SAMSmodified device with an outstanding fill factor of 0.84 delivers a significant improvement in efficiency(22.7%)in comparison with the control device(20.3%).The unencapsulated modified device demonstrates only little degradation after 1320 h at 60℃.
