Thunderstorm gusts are a common form of severe convective weather in the warm season in North China,and it is of great importance to correctly forecast them.At present,the forecasting of thunderstorm gusts is mainly b...Thunderstorm gusts are a common form of severe convective weather in the warm season in North China,and it is of great importance to correctly forecast them.At present,the forecasting of thunderstorm gusts is mainly based on traditional subjective methods,which fails to achieve high-resolution and high-frequency gridded forecasts based on multiple observation sources.In this paper,we propose a deep learning method called Thunderstorm Gusts TransU-net(TGTransUnet)to forecast thunderstorm gusts in North China based on multi-source gridded product data from the Institute of Urban Meteorology(IUM)with a lead time of 1 to 6 h.To determine the specific range of thunderstorm gusts,we combine three meteorological variables:radar reflectivity factor,lightning location,and 1-h maximum instantaneous wind speed from automatic weather stations(AWSs),and obtain a reasonable ground truth of thunderstorm gusts.Then,we transform the forecasting problem into an image-to-image problem in deep learning under the TG-TransUnet architecture,which is based on convolutional neural networks and a transformer.The analysis and forecast data of the enriched multi-source gridded comprehensive forecasting system for the period 2021–23 are then used as training,validation,and testing datasets.Finally,the performance of TG-TransUnet is compared with other methods.The results show that TG-TransUnet has the best prediction results at 1–6 h.The IUM is currently using this model to support the forecasting of thunderstorm gusts in North China.展开更多
TiO2 is the most photoactive material because of its superstrong photooxidizing ability,and TiO2 photocatalysis has been widely applied in sustainable water treatment and environmental remediation.However,poor sunligh...TiO2 is the most photoactive material because of its superstrong photooxidizing ability,and TiO2 photocatalysis has been widely applied in sustainable water treatment and environmental remediation.However,poor sunlight or visible-light harvesting efficiency and fast recombination rate of the photogenerated charge carriers severely limit the practical applications of TiO2.To overcome these problems,the present work demonstrates a facile in-situ co-condensation method combined with hydrothermal treatment to prepare a series of graphitized carbon/TiO2 composite photocatalysts,and anatase TiO2 phase andp-p-conjugated polycyclic aromatic carbon structure are created simultaneously.As-prepared TiO2/C composites exhibit remarkably high visible-light photocatalytic activity in the degradation of aqueous emerging phenolic pollutants,acetaminophen(APAP)and methylparaben(MPB),and apparent rate constant of the TiO2/C composite with carbon doping level of 10.3%for APAP and MPB removal is 7.6 and 2.8 times higher than that of bare TiO2,and 6.2 and 2.6 times higher than that of Degussa P25 TiO2.Based on the results of photoelectrochemical experiments,indirect chemical probe measurements,and ESR spectroscopy,it is verified that doping TiO2 with graphitized carbon is responsible for this enhanced photocatalytic activity,which renders the improved visible-light harvesting ability,the accelerated separation of the photogenerated charge carriers,and enlarged BET surface areas.Through analyzing the intermediates yielded in the photodegradation process,the pathway of visible-light photocatalytic degradation of APAP and MPB over the TiO2/C composite is proposed.展开更多
To carry out curriculum ideological and political education is to thoroughly implement the whole staff,the whole process,and all-round education.Taking the environmental chemistry course as an example,it introduces th...To carry out curriculum ideological and political education is to thoroughly implement the whole staff,the whole process,and all-round education.Taking the environmental chemistry course as an example,it introduces the feasibility of developing ideological and political education,and analyzes how to realize the integration of environmental chemistry courses and ideological and political education from the aspects of changing concepts,carefully designing teaching content,and playing the role of training courses and experimental courses.Integration has achieved certain results,providing reference and reference for environmental majors to carry out related courses ideological and political education.展开更多
The objective of this paper is to experimentally investigate the cavitation patterns and corresponding hydrodynamics of the hydrofoil with leading edge roughness.The aims are to(1)understand the effect of the leading ...The objective of this paper is to experimentally investigate the cavitation patterns and corresponding hydrodynamics of the hydrofoil with leading edge roughness.The aims are to(1)understand the effect of the leading edge roughness on the hydrodynamic performance,and(2)have a good knowledge of the interaction between the leading edge roughness and the cavitation patterns.Experimental results are indicated for the NACA 66 hydrofoils with and without leading edge roughness at different incidence angles for sub and cavitation conditions.The experiments are conducted in the EPFL high-speed cavitation tunnel(Avellan 2015).The results showed that the leading edge roughness has a significant effect on the hydrodynamic performance at the sub cavitation,suppressing the formation of the incipient cavitation.The lift coefficient of the hydrofoil without leading edge roughness is larger than that of the hydrofoil with leading edge roughness,while for the drag coefficients,the results are contrary for the lift coefficient,and the maximum lift-to-drag ratio angle is delayed for the hydrofoil with leading edge roughness.The leading edge roughness modified the local pressure distribution at the leading edge region,which in turn significantly increased the minimum pressure coefficient,hence the incipient cavitation number of the hydrofoil with leading edge roughness.The formation and evolution of the transient cavity for the cloud cavitation is little affected by the leading edge roughness.展开更多
Lately,in some regions and seasons in China,urban consumers have paid high in buying fresh agricultural products while farmers get unreasonable income from producing them.To seek the reason for the phenomenon and expl...Lately,in some regions and seasons in China,urban consumers have paid high in buying fresh agricultural products while farmers get unreasonable income from producing them.To seek the reason for the phenomenon and explore ways to simulate it,this study constructed and implemented a complex network model named the Bi-Level Multi-Local-World(BI-MLW model)with characteristics of an interdependent coupling relationship between its participants.To verify the validity of the model,this study implemented an experimental simulation under Small Decentralized Operation Mode(SDOM)and Large Centralized Operation Mode(LCOM)scenarios using Cucurbita pepo and Cucumber in the Tianjin area of China as sample empirical products.Results indicate that nodes do not increase edges rapidly which reflects that even large firms in agricultural business cannot occupy markets fleetly.Furthermore,under the SDOM scenario the BI-MLW model exposes scale-free features with a small average degree value and low average clustering coefficient,while under the LCOM scenario,the model displays a rising average clustering coefficient and a lowered average path length.Both of which are consistent with the common view in literature and features of reality.Thus,the BI-MLW model specially designed for fresh agricultural products supply chain can improve the descriptive ability than conventional Erdös-Rényi(ER),Barabási-Albert(BA),Bianconi-Barabási(BB)network models.展开更多
基金supported in part by the Beijing Natural Science Foundation(Grant No.8222051)the National Key R&D Program of China(Grant No.2022YFC3004103)+2 种基金the National Natural Foundation of China(Grant Nos.42275003 and 42275012)the China Meteorological Administration Key Innovation Team(Grant Nos.CMA2022ZD04 and CMA2022ZD07)the Beijing Science and Technology Program(Grant No.Z221100005222012).
文摘Thunderstorm gusts are a common form of severe convective weather in the warm season in North China,and it is of great importance to correctly forecast them.At present,the forecasting of thunderstorm gusts is mainly based on traditional subjective methods,which fails to achieve high-resolution and high-frequency gridded forecasts based on multiple observation sources.In this paper,we propose a deep learning method called Thunderstorm Gusts TransU-net(TGTransUnet)to forecast thunderstorm gusts in North China based on multi-source gridded product data from the Institute of Urban Meteorology(IUM)with a lead time of 1 to 6 h.To determine the specific range of thunderstorm gusts,we combine three meteorological variables:radar reflectivity factor,lightning location,and 1-h maximum instantaneous wind speed from automatic weather stations(AWSs),and obtain a reasonable ground truth of thunderstorm gusts.Then,we transform the forecasting problem into an image-to-image problem in deep learning under the TG-TransUnet architecture,which is based on convolutional neural networks and a transformer.The analysis and forecast data of the enriched multi-source gridded comprehensive forecasting system for the period 2021–23 are then used as training,validation,and testing datasets.Finally,the performance of TG-TransUnet is compared with other methods.The results show that TG-TransUnet has the best prediction results at 1–6 h.The IUM is currently using this model to support the forecasting of thunderstorm gusts in North China.
文摘TiO2 is the most photoactive material because of its superstrong photooxidizing ability,and TiO2 photocatalysis has been widely applied in sustainable water treatment and environmental remediation.However,poor sunlight or visible-light harvesting efficiency and fast recombination rate of the photogenerated charge carriers severely limit the practical applications of TiO2.To overcome these problems,the present work demonstrates a facile in-situ co-condensation method combined with hydrothermal treatment to prepare a series of graphitized carbon/TiO2 composite photocatalysts,and anatase TiO2 phase andp-p-conjugated polycyclic aromatic carbon structure are created simultaneously.As-prepared TiO2/C composites exhibit remarkably high visible-light photocatalytic activity in the degradation of aqueous emerging phenolic pollutants,acetaminophen(APAP)and methylparaben(MPB),and apparent rate constant of the TiO2/C composite with carbon doping level of 10.3%for APAP and MPB removal is 7.6 and 2.8 times higher than that of bare TiO2,and 6.2 and 2.6 times higher than that of Degussa P25 TiO2.Based on the results of photoelectrochemical experiments,indirect chemical probe measurements,and ESR spectroscopy,it is verified that doping TiO2 with graphitized carbon is responsible for this enhanced photocatalytic activity,which renders the improved visible-light harvesting ability,the accelerated separation of the photogenerated charge carriers,and enlarged BET surface areas.Through analyzing the intermediates yielded in the photodegradation process,the pathway of visible-light photocatalytic degradation of APAP and MPB over the TiO2/C composite is proposed.
文摘To carry out curriculum ideological and political education is to thoroughly implement the whole staff,the whole process,and all-round education.Taking the environmental chemistry course as an example,it introduces the feasibility of developing ideological and political education,and analyzes how to realize the integration of environmental chemistry courses and ideological and political education from the aspects of changing concepts,carefully designing teaching content,and playing the role of training courses and experimental courses.Integration has achieved certain results,providing reference and reference for environmental majors to carry out related courses ideological and political education.
基金The authors gratefully acknowledge the great help of Dr.Mohamed Farhat(EPFL-LMH)and the support by the National Natural Science Foundation of China(Grant Nos:51909002,51839001.and 91752105)the Fundamental Research Funds for the Central Universities,and the Open Fund for Key Laboratory of Fluid and Power Machinery,Ministry of Education(Grant Nos:szjj2018-124 and szjj2019-024).
文摘The objective of this paper is to experimentally investigate the cavitation patterns and corresponding hydrodynamics of the hydrofoil with leading edge roughness.The aims are to(1)understand the effect of the leading edge roughness on the hydrodynamic performance,and(2)have a good knowledge of the interaction between the leading edge roughness and the cavitation patterns.Experimental results are indicated for the NACA 66 hydrofoils with and without leading edge roughness at different incidence angles for sub and cavitation conditions.The experiments are conducted in the EPFL high-speed cavitation tunnel(Avellan 2015).The results showed that the leading edge roughness has a significant effect on the hydrodynamic performance at the sub cavitation,suppressing the formation of the incipient cavitation.The lift coefficient of the hydrofoil without leading edge roughness is larger than that of the hydrofoil with leading edge roughness,while for the drag coefficients,the results are contrary for the lift coefficient,and the maximum lift-to-drag ratio angle is delayed for the hydrofoil with leading edge roughness.The leading edge roughness modified the local pressure distribution at the leading edge region,which in turn significantly increased the minimum pressure coefficient,hence the incipient cavitation number of the hydrofoil with leading edge roughness.The formation and evolution of the transient cavity for the cloud cavitation is little affected by the leading edge roughness.
基金the support of Technology Innovation Project Fund of the Chinese Academy of Agricultural Sciences(CAAS-ASTIP-2020-AII-01)the Agricultural Monitoring and Early Warning Research Team of Agricultural Information Institute of Chinese Academy of Agricultural Sciences.
文摘Lately,in some regions and seasons in China,urban consumers have paid high in buying fresh agricultural products while farmers get unreasonable income from producing them.To seek the reason for the phenomenon and explore ways to simulate it,this study constructed and implemented a complex network model named the Bi-Level Multi-Local-World(BI-MLW model)with characteristics of an interdependent coupling relationship between its participants.To verify the validity of the model,this study implemented an experimental simulation under Small Decentralized Operation Mode(SDOM)and Large Centralized Operation Mode(LCOM)scenarios using Cucurbita pepo and Cucumber in the Tianjin area of China as sample empirical products.Results indicate that nodes do not increase edges rapidly which reflects that even large firms in agricultural business cannot occupy markets fleetly.Furthermore,under the SDOM scenario the BI-MLW model exposes scale-free features with a small average degree value and low average clustering coefficient,while under the LCOM scenario,the model displays a rising average clustering coefficient and a lowered average path length.Both of which are consistent with the common view in literature and features of reality.Thus,the BI-MLW model specially designed for fresh agricultural products supply chain can improve the descriptive ability than conventional Erdös-Rényi(ER),Barabási-Albert(BA),Bianconi-Barabási(BB)network models.
