A novel magnetic levitation support method is proposed, which can relieve the perturbation caused by traditional support methods andprovide more accurate position control of the capsule. This method can keep the perfe...A novel magnetic levitation support method is proposed, which can relieve the perturbation caused by traditional support methods andprovide more accurate position control of the capsule. This method can keep the perfect symmetry of the octahedral spherical hohlraum and hasthe characteristics in stability, tunability and simplicity. It is also favorable that all the results, such as supporting forces acting on the super-conducting capsule, are calculated analytically, and numerical simulations are performed to verify these results. A typical realistic design isproposed and discussed in detail. The superconducting coating material is suggested, and the required superconducting properties are listed.Damped oscillation of the floating capsule in thin helium gas is discussed, and the restoring time is estimated.展开更多
Oxygen vacancies in oxygen evolution cocatalysts(OECs)can significantly improve the photoelectrochemical(PEC)water splitting performance of photoanodes.However,OECs with abundant oxygen vacancies have a poor stability...Oxygen vacancies in oxygen evolution cocatalysts(OECs)can significantly improve the photoelectrochemical(PEC)water splitting performance of photoanodes.However,OECs with abundant oxygen vacancies have a poor stability when exposing to the highly-oxidizing photogenerated holes.Herein,we partly fill oxygen vacancies in a MnCo_(2)O_(x) OEC with N atoms by a combined electrodeposition and sol-gel method,which dramatically improves both photocurrent density and stability of a BiVO_(4) photoanode.The optimized N filled oxygen vacancy-rich MnCo_(2)O_(x)/BiVO_(4) photoanode(3 at.%of N)exhibits an outstanding photocurrent density of 6.5 mA·cm^(-2) at 1.23 VRHE under AM 1.5 G illumination(100 mW·cm^(-2)),and an excellent stability of over 150 h.Systematic characterizations and theoretical calculations demonstrate that N atoms stabilize the defect structure and modulate the surface electron distribution,which significantly enhances the stability and further increases the photocurrent density.Meanwhile,other heteroatoms such as carbon,phosphorus,and sulfur are confirmed to have similar effects on improving PEC water splitting performance of photoanodes.展开更多
Monthly precipitation over north China in August(NCAP)is the second highest in the year,and it is important to understand its driving mechanisms to facilitate reliable forecasting.The NCAP displays a significant decad...Monthly precipitation over north China in August(NCAP)is the second highest in the year,and it is important to understand its driving mechanisms to facilitate reliable forecasting.The NCAP displays a significant decadal variability of a cycle about 10-year and negatively correlates with the July north-east North Atlantic Tripole(NAT)over the decadal timescales.This study shows that the Eurasian decadal teleconnection(EAT)acts as a bridge that links the July NAT with NCAP decadal variability.This coupled ocean–atmosphere bridge(COAB)mechanism,through which the July NAT influences the decadal variability of NCAP,can be summarized as follows.The cumulative effect of the NAT drives the EAT to adjust atmospheric circulation over north China and the surrounding regions,and so regulates precipitation in north China by influencing local water vapor transport.When the July NAT is in a negative(positive)phase,the EAT pattern has a positive(negative)pattern,which promotes(weakens)the transmission of water vapor from the sea in the south-east to north China,thus increasing(decreasing)NCAP over decadal timescales.The decadal NCAP model established based on the July NAT can effectively predict the NCAP decadal variability,illustrating that the July NAT can be implicated as a predictor of the NCAP decadal variability.展开更多
A record-breaking extreme heavy snowfall(EHS)event hit northern China during 6–8 November 2021,with two maximum snowfall centers in North China(NC)and Northeast China(NEC),which inflicted severe socioeconomic impacts...A record-breaking extreme heavy snowfall(EHS)event hit northern China during 6–8 November 2021,with two maximum snowfall centers in North China(NC)and Northeast China(NEC),which inflicted severe socioeconomic impacts.This paper compares the differences in the synoptic processes and moisture supply associated with the EHS event in NC and NEC,as well as the atmospheric circulation anomalies before the event,to provide a reference for better prediction and forecasting of EHS in northern China.Synoptic analyses show that a positively tilted,inverted 500-hPa trough channeled cold-air outbreaks into NC,while dynamic updrafts along the front below the trough promoted moisture convergence over this region.In NEC,the dynamic updraft south of the frontogenesis region firstly triggered a low-level Yellow–Bohai Sea cyclone,which then converged with the 500-hPa trough to ultimately form an NEC cold vortex.Calculation of the vorticity tendency indicates that absolute vorticity advection was a better indicator than absolute vorticity divergence for the movement of the trough/ridge at the synoptic scale.Moreover,NOAA’s HYSPLIT(Hybrid Single-Particle Lagrangian Integrated Trajectory)model results reveal that the moisture for the EHS over NC mainly originated from the mid-to-low levels over the Asian–African region and the Eurasian mid-to-high latitudes,accounting for 32%and 31%,respectively.In contrast,the source of water vapor for the EHS over NEC was mainly the Eurasian mid-to-high latitudes and East Asia,with contributions of 38%and 28%,respectively.The findings of this study shed some fresh light on the distinctive contributions of different moisture sources to local precipitation.Further analyses of the atmospheric circulation anomalies in October reveal that a phase shift in the Arctic Oscillation related to the weakening of the polar vortex could have served as a useful indicator for the cold-air outbreaks in this EHS event.展开更多
Owing to the relatively short hole diffusion length,severe charge recombination in the bulk of bismuth vanadate(BiVO_(4))is the key issue for photoelectrochemical water splitting.Herein,we design a nanoporous MoO_(3−x...Owing to the relatively short hole diffusion length,severe charge recombination in the bulk of bismuth vanadate(BiVO_(4))is the key issue for photoelectrochemical water splitting.Herein,we design a nanoporous MoO_(3−x)/BiVO_(4)heterojunction photoanode to promote charge separation.The efficient electron transport properties of oxygen deficient MoO_(3−x)and the nanoporous structure are beneficial for charge separation,leading to a significantly enhanced PEC performance.The optimized MoO_(3−x)/BiVO_(4)heterojunction photoanode exhibits a photocurrent density of 5.07 mA·cm^(−2)for Na_(2)SO_(3)oxidation.By depositing FeOOH/NiOOH dual oxygen evolution cocatalysts to promote surface kinetics,a high photocurrent density of 4.81 mA·cm^(−2)can be achieved for PEC water splitting,exhibiting an excellent applied bias photon-to-current efficiency of 1.57%.Moreover,stable overall water splitting is achieved under consecutive light illumination for 10 h.We provide a proof of concept for the design of efficient BiVO_(4)-based heterojunction photoanodes for stable PEC water splitting.展开更多
文摘A novel magnetic levitation support method is proposed, which can relieve the perturbation caused by traditional support methods andprovide more accurate position control of the capsule. This method can keep the perfect symmetry of the octahedral spherical hohlraum and hasthe characteristics in stability, tunability and simplicity. It is also favorable that all the results, such as supporting forces acting on the super-conducting capsule, are calculated analytically, and numerical simulations are performed to verify these results. A typical realistic design isproposed and discussed in detail. The superconducting coating material is suggested, and the required superconducting properties are listed.Damped oscillation of the floating capsule in thin helium gas is discussed, and the restoring time is estimated.
基金The authors would like to acknowledge the financial support from National Natural Science Foundation of China(No.52002328)Shenzhen Science and Technology Program(No.JCYJ20220530161615035)+1 种基金the Practice and Innovation Funds for Graduate Students of Northwestern Polytechnical University(No.PF2023151)the Fundamental Research Funds for the Central Universities,and material characterizations from the Analytical&Testing Center of Northwestern Polytechnical University.
文摘Oxygen vacancies in oxygen evolution cocatalysts(OECs)can significantly improve the photoelectrochemical(PEC)water splitting performance of photoanodes.However,OECs with abundant oxygen vacancies have a poor stability when exposing to the highly-oxidizing photogenerated holes.Herein,we partly fill oxygen vacancies in a MnCo_(2)O_(x) OEC with N atoms by a combined electrodeposition and sol-gel method,which dramatically improves both photocurrent density and stability of a BiVO_(4) photoanode.The optimized N filled oxygen vacancy-rich MnCo_(2)O_(x)/BiVO_(4) photoanode(3 at.%of N)exhibits an outstanding photocurrent density of 6.5 mA·cm^(-2) at 1.23 VRHE under AM 1.5 G illumination(100 mW·cm^(-2)),and an excellent stability of over 150 h.Systematic characterizations and theoretical calculations demonstrate that N atoms stabilize the defect structure and modulate the surface electron distribution,which significantly enhances the stability and further increases the photocurrent density.Meanwhile,other heteroatoms such as carbon,phosphorus,and sulfur are confirmed to have similar effects on improving PEC water splitting performance of photoanodes.
基金supported by the Innovation and development project of China Meteorological Administration(No.CXFZ2021J030).
文摘Monthly precipitation over north China in August(NCAP)is the second highest in the year,and it is important to understand its driving mechanisms to facilitate reliable forecasting.The NCAP displays a significant decadal variability of a cycle about 10-year and negatively correlates with the July north-east North Atlantic Tripole(NAT)over the decadal timescales.This study shows that the Eurasian decadal teleconnection(EAT)acts as a bridge that links the July NAT with NCAP decadal variability.This coupled ocean–atmosphere bridge(COAB)mechanism,through which the July NAT influences the decadal variability of NCAP,can be summarized as follows.The cumulative effect of the NAT drives the EAT to adjust atmospheric circulation over north China and the surrounding regions,and so regulates precipitation in north China by influencing local water vapor transport.When the July NAT is in a negative(positive)phase,the EAT pattern has a positive(negative)pattern,which promotes(weakens)the transmission of water vapor from the sea in the south-east to north China,thus increasing(decreasing)NCAP over decadal timescales.The decadal NCAP model established based on the July NAT can effectively predict the NCAP decadal variability,illustrating that the July NAT can be implicated as a predictor of the NCAP decadal variability.
基金Supported by the National Key Research and Development Program of China(2018YFC1505604)Innovation and Development Project of China Meteorological Administration(CXFZ2021J022).
文摘A record-breaking extreme heavy snowfall(EHS)event hit northern China during 6–8 November 2021,with two maximum snowfall centers in North China(NC)and Northeast China(NEC),which inflicted severe socioeconomic impacts.This paper compares the differences in the synoptic processes and moisture supply associated with the EHS event in NC and NEC,as well as the atmospheric circulation anomalies before the event,to provide a reference for better prediction and forecasting of EHS in northern China.Synoptic analyses show that a positively tilted,inverted 500-hPa trough channeled cold-air outbreaks into NC,while dynamic updrafts along the front below the trough promoted moisture convergence over this region.In NEC,the dynamic updraft south of the frontogenesis region firstly triggered a low-level Yellow–Bohai Sea cyclone,which then converged with the 500-hPa trough to ultimately form an NEC cold vortex.Calculation of the vorticity tendency indicates that absolute vorticity advection was a better indicator than absolute vorticity divergence for the movement of the trough/ridge at the synoptic scale.Moreover,NOAA’s HYSPLIT(Hybrid Single-Particle Lagrangian Integrated Trajectory)model results reveal that the moisture for the EHS over NC mainly originated from the mid-to-low levels over the Asian–African region and the Eurasian mid-to-high latitudes,accounting for 32%and 31%,respectively.In contrast,the source of water vapor for the EHS over NEC was mainly the Eurasian mid-to-high latitudes and East Asia,with contributions of 38%and 28%,respectively.The findings of this study shed some fresh light on the distinctive contributions of different moisture sources to local precipitation.Further analyses of the atmospheric circulation anomalies in October reveal that a phase shift in the Arctic Oscillation related to the weakening of the polar vortex could have served as a useful indicator for the cold-air outbreaks in this EHS event.
基金the National Natural Science Foundation of China(No.52002328)the Fundamental Research Funds for the Central Universities,the Joint Research Funds of Department of Science&Technology of Shaanxi Province,and Northwestern Polytechnical University(No.2020GXLH-Z-018).
文摘Owing to the relatively short hole diffusion length,severe charge recombination in the bulk of bismuth vanadate(BiVO_(4))is the key issue for photoelectrochemical water splitting.Herein,we design a nanoporous MoO_(3−x)/BiVO_(4)heterojunction photoanode to promote charge separation.The efficient electron transport properties of oxygen deficient MoO_(3−x)and the nanoporous structure are beneficial for charge separation,leading to a significantly enhanced PEC performance.The optimized MoO_(3−x)/BiVO_(4)heterojunction photoanode exhibits a photocurrent density of 5.07 mA·cm^(−2)for Na_(2)SO_(3)oxidation.By depositing FeOOH/NiOOH dual oxygen evolution cocatalysts to promote surface kinetics,a high photocurrent density of 4.81 mA·cm^(−2)can be achieved for PEC water splitting,exhibiting an excellent applied bias photon-to-current efficiency of 1.57%.Moreover,stable overall water splitting is achieved under consecutive light illumination for 10 h.We provide a proof of concept for the design of efficient BiVO_(4)-based heterojunction photoanodes for stable PEC water splitting.