Taking five scenic spots in southeast region of Tibet as research objects,this paper calculated the weight of plant landscape evaluation system by entropy weight method,and compared the plant landscape in scenic spots...Taking five scenic spots in southeast region of Tibet as research objects,this paper calculated the weight of plant landscape evaluation system by entropy weight method,and compared the plant landscape in scenic spots from aesthetic effect,ecological harmony and service functions. The results show that the rank of the comprehensive attributes from high to low is as follows: Nanyigou,Lulang Forest,Kading Mountain Waterfall,Yarlung Zangbo Grand Canyon,and Basomtso Lake.展开更多
The g-C_(3)N_(4)/BiOI/CdS double Z-scheme heterojunction photocatalyst with I_(3)^(-)/I^(-) redox pairs is prepared using simple calcination,solvothermal,and solution chemical deposition methods.The photocatalyst comp...The g-C_(3)N_(4)/BiOI/CdS double Z-scheme heterojunction photocatalyst with I_(3)^(-)/I^(-) redox pairs is prepared using simple calcination,solvothermal,and solution chemical deposition methods.The photocatalyst comprised mesoporous,thin g-C_(3)N_(4) nanosheets loaded on flower-like microspheres of BiOI with CdS quantum dots.The g-C_(3)N_(4)/BiOI/CdS double Z-scheme heterojunction has abundant active sites and in situ redox I_(3)^(-)/I^(-) mediators and shows quantum size effects,which are all conducive to enhancing the separation of photoinduced charges and increasing the photocatalytic degradation efficiency for bisphenol A,a model pollutant.Specifically,the heterojunction photocatalyst achieves a photocatalytic degradation efficiency for bisphenol A of 98.62%in 120 min and photocatalytic hydrogen production of 863.44 mmol h^(-1) g^(-1) on exposure to visible light.The excellent visible-light photocatalytic performance is as a result of the Z-scheme heterojunction,which extends absorption to the visible light region,as well as the I_(3)^(-)/I^(-) pairs,which accelerate photoinduced charge carrier transfer and separation,thus dramatically boosting the photocatalytic performance.In addition,the key role of the charge transfer across the indirect Z-scheme heterojunction has been elucidated and the transfer mechanism is confirmed based on the detection of intermediate I_(3)^(-)ions.Thus,this study provides guidelines for the design of indirect Z-scheme heterojunction photocatalysts.展开更多
Over the years,the logistics development in Tibet has fallen behind the transport. Since the opening of Qinghai-Tibet Railway in2006,the opportunity for development of modern logistics has been brought to Tibet. The l...Over the years,the logistics development in Tibet has fallen behind the transport. Since the opening of Qinghai-Tibet Railway in2006,the opportunity for development of modern logistics has been brought to Tibet. The logistics demand analysis and forecasting is a prerequisite for regional logistics planning. By establishing indicator system for logistics demand of agricultural products,agricultural product logistics principal component regression model,gray forecasting model,BP neural network forecasting model are built. Because of the single model's limitations,quadratic-linear programming model is used to build combination forecasting model to predict the logistics demand scale of agricultural products in Tibet over the next five years. The empirical analysis results show that combination forecasting model is superior to single forecasting model,and it has higher precision,so combination forecasting model will have much wider application foreground and development potential in the field of logistics.展开更多
Antiferromagnetic imaging is critical for understanding and optimizing the properties of antiferromagnetic materials and devices.Despite the widespread use of high-energy electrons for atomic-scale imaging,they have l...Antiferromagnetic imaging is critical for understanding and optimizing the properties of antiferromagnetic materials and devices.Despite the widespread use of high-energy electrons for atomic-scale imaging,they have low sensitivity to spin textures.Typically,the magnetic contribution to the phase of a highenergy electron wave is weaker than one percent of the electrostatic potential.Here,we demonstrate direct imaging of antiferromagnetic lattice through precise phase retrieval via electron ptychography,paving the way for magnetic lattice imaging of antiferromagnetic materials and devices.展开更多
基金Supported by Project of National Natural Science Foundation(71263048)
文摘Taking five scenic spots in southeast region of Tibet as research objects,this paper calculated the weight of plant landscape evaluation system by entropy weight method,and compared the plant landscape in scenic spots from aesthetic effect,ecological harmony and service functions. The results show that the rank of the comprehensive attributes from high to low is as follows: Nanyigou,Lulang Forest,Kading Mountain Waterfall,Yarlung Zangbo Grand Canyon,and Basomtso Lake.
基金support of this work by the National Natural Science Foundation of China(51869006)Jiangxi Natural Science Foundation of China(20171BAB216050)Water Science and Technology Fund of Jiangxi Province in China(KT201702).
文摘The g-C_(3)N_(4)/BiOI/CdS double Z-scheme heterojunction photocatalyst with I_(3)^(-)/I^(-) redox pairs is prepared using simple calcination,solvothermal,and solution chemical deposition methods.The photocatalyst comprised mesoporous,thin g-C_(3)N_(4) nanosheets loaded on flower-like microspheres of BiOI with CdS quantum dots.The g-C_(3)N_(4)/BiOI/CdS double Z-scheme heterojunction has abundant active sites and in situ redox I_(3)^(-)/I^(-) mediators and shows quantum size effects,which are all conducive to enhancing the separation of photoinduced charges and increasing the photocatalytic degradation efficiency for bisphenol A,a model pollutant.Specifically,the heterojunction photocatalyst achieves a photocatalytic degradation efficiency for bisphenol A of 98.62%in 120 min and photocatalytic hydrogen production of 863.44 mmol h^(-1) g^(-1) on exposure to visible light.The excellent visible-light photocatalytic performance is as a result of the Z-scheme heterojunction,which extends absorption to the visible light region,as well as the I_(3)^(-)/I^(-) pairs,which accelerate photoinduced charge carrier transfer and separation,thus dramatically boosting the photocatalytic performance.In addition,the key role of the charge transfer across the indirect Z-scheme heterojunction has been elucidated and the transfer mechanism is confirmed based on the detection of intermediate I_(3)^(-)ions.Thus,this study provides guidelines for the design of indirect Z-scheme heterojunction photocatalysts.
基金Supported by National Natural Science Foundation(71263048)Project of Tibe Autonomous Region Department of Education(2013ZJRW142013ZJJG11)
文摘Over the years,the logistics development in Tibet has fallen behind the transport. Since the opening of Qinghai-Tibet Railway in2006,the opportunity for development of modern logistics has been brought to Tibet. The logistics demand analysis and forecasting is a prerequisite for regional logistics planning. By establishing indicator system for logistics demand of agricultural products,agricultural product logistics principal component regression model,gray forecasting model,BP neural network forecasting model are built. Because of the single model's limitations,quadratic-linear programming model is used to build combination forecasting model to predict the logistics demand scale of agricultural products in Tibet over the next five years. The empirical analysis results show that combination forecasting model is superior to single forecasting model,and it has higher precision,so combination forecasting model will have much wider application foreground and development potential in the field of logistics.
基金supported by the National Natural Science Foundation of China(52388201 and 51525102)the support from the Physical Sciences Center and Center of High-Performance Computing,Tsinghua University.
文摘Antiferromagnetic imaging is critical for understanding and optimizing the properties of antiferromagnetic materials and devices.Despite the widespread use of high-energy electrons for atomic-scale imaging,they have low sensitivity to spin textures.Typically,the magnetic contribution to the phase of a highenergy electron wave is weaker than one percent of the electrostatic potential.Here,we demonstrate direct imaging of antiferromagnetic lattice through precise phase retrieval via electron ptychography,paving the way for magnetic lattice imaging of antiferromagnetic materials and devices.
