Short-duration snow bursts with heavy snow represent one type of hazardous weather in winter which can be easily missed by the winter weather warnings but often results in great hazards.In this paper,the mechanism for...Short-duration snow bursts with heavy snow represent one type of hazardous weather in winter which can be easily missed by the winter weather warnings but often results in great hazards.In this paper,the mechanism for the occurrence of such events was investigated with the aid of a localized terrain-influenced snow burst event in Northeast China.The snow burst was produced by an eastward-moving cold-frontal snowband which encountered the downstream complex terrain of the Changbai Mountains and intensified.To ascertain the role of orography on the snow burst,numerical experiments,together with a parallel sensitivity experiment removing Changbai Mountains,were performed to attempt to distinguish the contributions of cold-frontal system and orographic effects to produce the heavy snow.Diagnosis showed that without the influence of Changbai Mountains,the release of conditional instability(CI)and inertial instability(II)within a weak frontogenetical environment was responsible for the snowband maintenance.Orographic effects played important roles in enhancing the snowband and increasing the snowfall intensities.The enhancement mechanism was related to the interactions of the cold-frontal snowband and the topography.On the one hand,orographic frontogenesis and persistent ascent,created by orographic gravity waves over the terrain,greatly enhanced the orographic lifting.The intensification of the lifting promoted the release of CI and thus enhanced the snowfall.On the other hand,pre-existing orographic instabilities were released due to the passing of the cold-frontal snowband,which could also serve to intensify the snowband over terrain and thus increase the snowfall.展开更多
Electrochemical oxygen evolution reaction (OER) is a main efficiency bottleneck of water electrolysis.Commercial ruthenium oxide (RuO_(2)) catalyst displays remarkable activities but poor stability for OER.The instabi...Electrochemical oxygen evolution reaction (OER) is a main efficiency bottleneck of water electrolysis.Commercial ruthenium oxide (RuO_(2)) catalyst displays remarkable activities but poor stability for OER.The instability stems from lattice oxygen oxidation,resulting in the oxidation of Ru^(4+) to soluble Ru^(4+)(x>4) species.Herein,we redirect dynamic structural evolution of Ru-based catalysts through introducing oxidized nickel (Ni) components.By virtue of comprehensive structural characterizations,such as high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM),X-ray photoelectron spectroscopy (XPS),operando Raman and so forth,it is demonstrated that when the atomic content of Ni exceeds that of ruthenium (Ru),the Ni components can efficiently inhibit the Ru^(4+) oxidation and structural collapse.Density functional theory (DFT) calculations suggest that the introduction of Ni component hinders the formation of oxygen vacancies,and makes lattice oxygen mediated mechanism turn to adsorbate evolution mechanism,which eventually improves the stability.The optimized nickel-contained RuO_(2) catalyst delivers an effective reactivity with an overpotential of less than 215 m V to attain 10 m A cm^(-2) and remarkable stability with only 5 mV increment after 5000 potential cycles.This work provides insights into the origin of dynamic structural evolution of transition-metalmodified RuO_(2) electrocatalysts.展开更多
A snow burst event characterized by brief heavy snowfall affected Northeast China and caused serious social impact on 26 January 2017,with the snowband generally aligned with a northeast–southwest-oriented cold front...A snow burst event characterized by brief heavy snowfall affected Northeast China and caused serious social impact on 26 January 2017,with the snowband generally aligned with a northeast–southwest-oriented cold front.ECMWF reanalysis data were used to diagnose the possible trigger mechanism.Results showed there were two stages:(a)an initial stage far away from the Changbai Mountains,and(b)an enhancement stage under the influence of high terrain.During the initial stage,the coupling of low-level frontogenesis and a favorable convergence pattern caused strong upward motion,contributing to the release of instability.When the snowband approached the high terrain during the enhancement stage,the various instabilities were triggered by the low-level frontogenesis,terrain circulation,and strong wind shear associated with the low-level jet.Further,a modified Q-vector divergence including generalized potential temperature was calculated to diagnose the vertical motion.It showed that the frontogenesis terms contributed greatly to the negative Q-vector divergence along the moist isentropes,while the pseudo-vorticity terms played a role in the regions with strong wind shear associated with the low-level jet in the warm section,suggesting both were important in stimulating the ascending motion.The regions with negative Q-vector divergence had a close relationship with the vertical structure of convection,indicating the potential to track the development of the snowband in the next few hours.展开更多
With the people's lives improving,the demands of livestock products on the import and export aspects were growing. Veterinary drug residues as the important factor which might influence animal products safety has ...With the people's lives improving,the demands of livestock products on the import and export aspects were growing. Veterinary drug residues as the important factor which might influence animal products safety has become a major concern. In this paper,the status quo and inspection of the veterinary drug residue and the corresponding control measures were put forward.展开更多
Quality and safety of agricultural products are significant for national socioeconomic development,sustainable development,and vital interests of people.To safeguard quality and safety of agricultural products in west...Quality and safety of agricultural products are significant for national socioeconomic development,sustainable development,and vital interests of people.To safeguard quality and safety of agricultural products in west China is to safeguard economic safety and ecological safety of the country,public health and social stability,of which an important task is to properly handle emergencies concerning quality and safety of agricultural products.Considering actual conditions of west China,suggestions are given to construct the all-region linkage system for emergency management of agricultural product quality and safety in the local area,enhance the all-region linkage,and improve the linkage efficiency.展开更多
Transition metal-N-C materials have considerably been demonstrated as promising catalysts for cathodic oxygen reduction reaction(ORR)in Zn-air batteries.Current efforts mainly focus on tailoring coordination structure...Transition metal-N-C materials have considerably been demonstrated as promising catalysts for cathodic oxygen reduction reaction(ORR)in Zn-air batteries.Current efforts mainly focus on tailoring coordination structure and identifying active sites of metal-N-C materials for ORR,while the mass transport of metal-N-C employed in catalytic layers of working electrodes is seldom engineered.Herein,a Fe-N-C single-atom catalyst featuring high mesoporosity and abundant electrochemically accessible active sites is developed through post-loading Fe species into defective N-doped carbon support.The Fe-N-C single-atom catalyst serving as the air cathode of Zn-air battery delivers a peak power density of 189.9 mW cm^(−2),significantly larger than 114.2 mW cm^(−2) of commercial Pt/C and 162.9 mW cm^(−2) of the Fe-N-C contrast catalyst with low mesoporosity.More importantly,through adding hydrophobic polytetrafluoroethylene(PTFE)nanoparticles in the catalytic layer of air cathode,the peak power density of Fe-N-C single-atom catalyst is further increased to 212.3 mW cm^(−2).The increased peak power density is attributed to the enhancement of O_(2) mass transport,as evidenced by a substantially decreased diffusion layer thickness that is obtained from electrochemical impedance spectroscopy.展开更多
基金the Chinese Academy of Sciences(Grant No.XDA17010105)the National Key Research and Development Project(Grant No.2018YFC1507104)+2 种基金The Key Scientific and Technology Research and Development Program of Jilin Province(Grant No.20180201035SF)the National Natural Science Foundation of China(Grant Nos.41875056,41575065 and 41790471,42075013)Chongqing Technology Innovation and Application Development Special Key Project(Grant No.cstc2019jscxtjsbX0007).
文摘Short-duration snow bursts with heavy snow represent one type of hazardous weather in winter which can be easily missed by the winter weather warnings but often results in great hazards.In this paper,the mechanism for the occurrence of such events was investigated with the aid of a localized terrain-influenced snow burst event in Northeast China.The snow burst was produced by an eastward-moving cold-frontal snowband which encountered the downstream complex terrain of the Changbai Mountains and intensified.To ascertain the role of orography on the snow burst,numerical experiments,together with a parallel sensitivity experiment removing Changbai Mountains,were performed to attempt to distinguish the contributions of cold-frontal system and orographic effects to produce the heavy snow.Diagnosis showed that without the influence of Changbai Mountains,the release of conditional instability(CI)and inertial instability(II)within a weak frontogenetical environment was responsible for the snowband maintenance.Orographic effects played important roles in enhancing the snowband and increasing the snowfall intensities.The enhancement mechanism was related to the interactions of the cold-frontal snowband and the topography.On the one hand,orographic frontogenesis and persistent ascent,created by orographic gravity waves over the terrain,greatly enhanced the orographic lifting.The intensification of the lifting promoted the release of CI and thus enhanced the snowfall.On the other hand,pre-existing orographic instabilities were released due to the passing of the cold-frontal snowband,which could also serve to intensify the snowband over terrain and thus increase the snowfall.
基金supported by the National Natural Science Foundation of China (21978278, 21838003 and 91834301)the Shanghai Scientific and Technological Innovation Project (18JC1410500 and 19JC1410400)the Fundamental Research Funds for the Central Universities (222201718002)。
文摘Electrochemical oxygen evolution reaction (OER) is a main efficiency bottleneck of water electrolysis.Commercial ruthenium oxide (RuO_(2)) catalyst displays remarkable activities but poor stability for OER.The instability stems from lattice oxygen oxidation,resulting in the oxidation of Ru^(4+) to soluble Ru^(4+)(x>4) species.Herein,we redirect dynamic structural evolution of Ru-based catalysts through introducing oxidized nickel (Ni) components.By virtue of comprehensive structural characterizations,such as high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM),X-ray photoelectron spectroscopy (XPS),operando Raman and so forth,it is demonstrated that when the atomic content of Ni exceeds that of ruthenium (Ru),the Ni components can efficiently inhibit the Ru^(4+) oxidation and structural collapse.Density functional theory (DFT) calculations suggest that the introduction of Ni component hinders the formation of oxygen vacancies,and makes lattice oxygen mediated mechanism turn to adsorbate evolution mechanism,which eventually improves the stability.The optimized nickel-contained RuO_(2) catalyst delivers an effective reactivity with an overpotential of less than 215 m V to attain 10 m A cm^(-2) and remarkable stability with only 5 mV increment after 5000 potential cycles.This work provides insights into the origin of dynamic structural evolution of transition-metalmodified RuO_(2) electrocatalysts.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences grant numbers XDA17010105and XDA20100304the National Key Research and Development Program grant numbers 2018YFC1507104 and 2019YFC1510400+1 种基金the Key Projects of Jilin Province Science and Technology Development Plan grant numbers 20180201035SFthe National Natural Science Foundation of China grant numbers 41775140 and 41790471。
文摘A snow burst event characterized by brief heavy snowfall affected Northeast China and caused serious social impact on 26 January 2017,with the snowband generally aligned with a northeast–southwest-oriented cold front.ECMWF reanalysis data were used to diagnose the possible trigger mechanism.Results showed there were two stages:(a)an initial stage far away from the Changbai Mountains,and(b)an enhancement stage under the influence of high terrain.During the initial stage,the coupling of low-level frontogenesis and a favorable convergence pattern caused strong upward motion,contributing to the release of instability.When the snowband approached the high terrain during the enhancement stage,the various instabilities were triggered by the low-level frontogenesis,terrain circulation,and strong wind shear associated with the low-level jet.Further,a modified Q-vector divergence including generalized potential temperature was calculated to diagnose the vertical motion.It showed that the frontogenesis terms contributed greatly to the negative Q-vector divergence along the moist isentropes,while the pseudo-vorticity terms played a role in the regions with strong wind shear associated with the low-level jet in the warm section,suggesting both were important in stimulating the ascending motion.The regions with negative Q-vector divergence had a close relationship with the vertical structure of convection,indicating the potential to track the development of the snowband in the next few hours.
基金Supported by Scientific and Technological Program in State Quality Detection Bureau(2088IK013,2010IK004)Key Scientic techndogical Program(2012ZRZ014,2012SZZ030)
文摘With the people's lives improving,the demands of livestock products on the import and export aspects were growing. Veterinary drug residues as the important factor which might influence animal products safety has become a major concern. In this paper,the status quo and inspection of the veterinary drug residue and the corresponding control measures were put forward.
基金Supported by AQSIQ Scientific Program Research on Coutermeasures for TBT of Pork Export2012 Sichuan Provincial Key Self-sponsored Sci-tech Program(2012ZRZ014,2012SZZ030)2013 Sci-tech Program of Sichuan Entry Exit Inspection and Quarantine Bureau(SK201314)
文摘Quality and safety of agricultural products are significant for national socioeconomic development,sustainable development,and vital interests of people.To safeguard quality and safety of agricultural products in west China is to safeguard economic safety and ecological safety of the country,public health and social stability,of which an important task is to properly handle emergencies concerning quality and safety of agricultural products.Considering actual conditions of west China,suggestions are given to construct the all-region linkage system for emergency management of agricultural product quality and safety in the local area,enhance the all-region linkage,and improve the linkage efficiency.
基金the National Key R&D Program of China(2022YFB3808400)the National Natural Science Foundation of China(22222804 and U22B20143)+1 种基金the Science and Technology Commission of Shanghai Municipality(22dz1205900)the Shanghai Municipal Science and Technology Major Project。
基金supported by the National Natural Science Foundation of China(21838003,91834301,21978278,21978087)the Shanghai Scientific and Technological Innovation Project(18JC1410500,19JC1410400)the Fundamental Research Funds for the Central Universities(222201718002)。
文摘Transition metal-N-C materials have considerably been demonstrated as promising catalysts for cathodic oxygen reduction reaction(ORR)in Zn-air batteries.Current efforts mainly focus on tailoring coordination structure and identifying active sites of metal-N-C materials for ORR,while the mass transport of metal-N-C employed in catalytic layers of working electrodes is seldom engineered.Herein,a Fe-N-C single-atom catalyst featuring high mesoporosity and abundant electrochemically accessible active sites is developed through post-loading Fe species into defective N-doped carbon support.The Fe-N-C single-atom catalyst serving as the air cathode of Zn-air battery delivers a peak power density of 189.9 mW cm^(−2),significantly larger than 114.2 mW cm^(−2) of commercial Pt/C and 162.9 mW cm^(−2) of the Fe-N-C contrast catalyst with low mesoporosity.More importantly,through adding hydrophobic polytetrafluoroethylene(PTFE)nanoparticles in the catalytic layer of air cathode,the peak power density of Fe-N-C single-atom catalyst is further increased to 212.3 mW cm^(−2).The increased peak power density is attributed to the enhancement of O_(2) mass transport,as evidenced by a substantially decreased diffusion layer thickness that is obtained from electrochemical impedance spectroscopy.
