Although convection embedded in stratiform cloud is often disordered, it is ordered under certain weather conditions. In particular, there are two forms of ordered convection: embedded convection with a ladder-like pa...Although convection embedded in stratiform cloud is often disordered, it is ordered under certain weather conditions. In particular, there are two forms of ordered convection: embedded convection with a ladder-like pattern and that with a parallel pattern. However, there is little literature regarding these patterns. Because stratiform clouds with embedded convection are major objects for weather-modification studies, it is important to explore the formation/development and characteristic precipitation of embedded convection from the perspective of cloud and precipitation physics. In this paper, using observation data, we simulate a large-scale precipitation event in China for July 19-21, 2007, employing the mesoscale Weather Research and Forecasting (WRF) model (V2.2). The rainfall-related clouds are analyzed through simulation, with particular focus being given to the genesis of embedded convection, the precipitation and microphysical properties. The results show that the WRF model can simulate features of this kind of nephsystem, indicating a close relationship between convection genesis and the 500 hPa trough and low-level convergence line. In such a favorable weather situation, there are two ordered patterns of embedded con- vection in the nephsystem, one being a group of convection centers arranged at different altitudes in a ladder-like manner and the other being a group of convection centers with a parallel pattern. In the first case, rainfall also has a ladder feature, with precipitation being highest for the top convection and reducing to the base convection. This implies that the higher the convection develops, the more active the microphysics in warmand cold-cloud processes is, leading to greater precipitation; i.e. rainfall in a ladder-like distribution. In the second case, rainfall decreases step by step from south to north, with the precipitation depending strongly on the cloud-water content therein. The two patterns of embedded convection and their precipitation features and microphysics are intensively studied from a new point of view.展开更多
Regarding conventional quantum dot lightemitting diodes(QLEDs)fabricated by using the spin-coating(SC)technique,voids and interstitial spaces are inevitable due to unordered quantum dots(QDs)stacking,generating device...Regarding conventional quantum dot lightemitting diodes(QLEDs)fabricated by using the spin-coating(SC)technique,voids and interstitial spaces are inevitable due to unordered quantum dots(QDs)stacking,generating device leakage current under an external bias.In the present study,we fabricated an ultra-homogeneous and highly ordered QD monolayer by adopting the Langmuir-Blodgett(LB)technique.The QD monolayer was transferred as a emissive layer with a horizontal lifting(HL)method to a red QLED,which exhibited high performance with an external quantum efficiency(EQE)of 19.0% and lifetime(T_(95)@100 cd m^(-2))of13,324 h.When compared with the SC-based device,the EQE and lifetime were improved by 15% and 183% due to the compact and ordered QD monolayer that lowered the leakage current.Moreover,white QLEDs with stacked QD monolayers could be obtained at a low voltage of 4 V because LB technique is an organic-solvent-free approach avoiding interlayer mixing and controlling the QD layer thickness precisely.In addition,we successfully fabricated an ultra-homogeneous large-area QD monolayer on a rectangular substrate with a size of 9 cm×5 cm,indicating the promising size scalability of the LB-HL strategy.展开更多
基金supported by National Natural Science Foundation of China (Grant Nos. 40975086 and 40537034)the National Research Project of the Scientific & Technical Support (Grant No. 2006BAC12B02)
文摘Although convection embedded in stratiform cloud is often disordered, it is ordered under certain weather conditions. In particular, there are two forms of ordered convection: embedded convection with a ladder-like pattern and that with a parallel pattern. However, there is little literature regarding these patterns. Because stratiform clouds with embedded convection are major objects for weather-modification studies, it is important to explore the formation/development and characteristic precipitation of embedded convection from the perspective of cloud and precipitation physics. In this paper, using observation data, we simulate a large-scale precipitation event in China for July 19-21, 2007, employing the mesoscale Weather Research and Forecasting (WRF) model (V2.2). The rainfall-related clouds are analyzed through simulation, with particular focus being given to the genesis of embedded convection, the precipitation and microphysical properties. The results show that the WRF model can simulate features of this kind of nephsystem, indicating a close relationship between convection genesis and the 500 hPa trough and low-level convergence line. In such a favorable weather situation, there are two ordered patterns of embedded con- vection in the nephsystem, one being a group of convection centers arranged at different altitudes in a ladder-like manner and the other being a group of convection centers with a parallel pattern. In the first case, rainfall also has a ladder feature, with precipitation being highest for the top convection and reducing to the base convection. This implies that the higher the convection develops, the more active the microphysics in warmand cold-cloud processes is, leading to greater precipitation; i.e. rainfall in a ladder-like distribution. In the second case, rainfall decreases step by step from south to north, with the precipitation depending strongly on the cloud-water content therein. The two patterns of embedded convection and their precipitation features and microphysics are intensively studied from a new point of view.
基金supported by the National Natural Science Foundation of China(62075043)Fujian Science&Technology Innovation Laboratory for Optoelectronic Information of China(2021ZZ126)。
文摘Regarding conventional quantum dot lightemitting diodes(QLEDs)fabricated by using the spin-coating(SC)technique,voids and interstitial spaces are inevitable due to unordered quantum dots(QDs)stacking,generating device leakage current under an external bias.In the present study,we fabricated an ultra-homogeneous and highly ordered QD monolayer by adopting the Langmuir-Blodgett(LB)technique.The QD monolayer was transferred as a emissive layer with a horizontal lifting(HL)method to a red QLED,which exhibited high performance with an external quantum efficiency(EQE)of 19.0% and lifetime(T_(95)@100 cd m^(-2))of13,324 h.When compared with the SC-based device,the EQE and lifetime were improved by 15% and 183% due to the compact and ordered QD monolayer that lowered the leakage current.Moreover,white QLEDs with stacked QD monolayers could be obtained at a low voltage of 4 V because LB technique is an organic-solvent-free approach avoiding interlayer mixing and controlling the QD layer thickness precisely.In addition,we successfully fabricated an ultra-homogeneous large-area QD monolayer on a rectangular substrate with a size of 9 cm×5 cm,indicating the promising size scalability of the LB-HL strategy.
