Solution‐processed perovskite‐based light‐emitting diodes (PeLEDs) are promising candidates for low‐cost, large‐area displays, while severe deterioration of the perovskite light‐emitting layer occurs during deposition of electron transport layers from solution in an issue. Herein, core/shell ZnO/ZnS nanoparticles as a solution‐processed electron transport layer in PeLED based on quasi‐2D PEA2Csn−1PbnBr3n+1 (PEA = phenylethylammonium) perovskite are employed. The deposition of ZnS shell mitigates trap states on ZnO core by anchoring sulfur to oxygen vacancies, and at the same time removes residual hydroxyl groups, which helps to suppress the interfacial trap‐assisted non‐radiative recombination and the deprotonation reaction between the perovskite layer and ZnO. The core/shell ZnO/ZnS nanoparticles show comparably high electron mobility to pristine ZnO nanoparticles, combined with the reduced energy barrier between the electron transport layer and the perovskite layer, improving the charge injection balance in PeLEDs. As a result, the optimized PeLEDs employing core/shell ZnO/ZnS nanoparticles as a solution‐processed electron transport layer exhibit high peak luminance reaching 32 400 cd m−2, external quantum efficiency of 10.3%, and 20‐fold extended longevity as compared to the devices utilizing ZnO nanoparticles, which represents one of the highest overall performances for solution‐processed PeLEDs.
Sky cloud detection has a significant application value in the meteorological field. The existing cloud detection methods mainly rely on the color difference between the sky background and the cloud layer in the sky image and are not reliable due to the variable and irregular characteristics of the cloud layer and different weather conditions. This paper proposes a cloud detection method based on all-sky polarization imaging. The core of the algorithm is the “normalized polarization degree difference index” (NPDDI). Instead of relying on the color difference information, this index identifies the difference between degree of polarization (DoPs) of the cloud sky and the clear sky radiation to achieve cloud recognition. The method is not only fast and straightforward in the algorithm, but also can detect the optical thickness of the cloud layer in a qualitative sense. The experimental results show a good cloud detection performance.
As an important infrastructure, road has attracted a lot of attentions in recent years. Most of current road information extraction methods rely on either elaborate algorithms or complex equipment. This manuscript proposes a simple and rapid image mosaic method to extract road surface based on a monocular camera. First, key frames are extracted to remove redundant information from image sequences. To eliminate perspective effect, extracted key frames are transformed into top view of road images based on inverse perspective mapping algorithm with the help of an attitude tensor. Then, a coarse-to-fine registration strategy is proposed to align all transformed key frames into a unified coordinate system. Finally, considering the specificity of transformed images, a superposing and overlapping image fusion strategy is proposed to alleviate the effect of stitching seam. The experiments are conducted on a road with the size of 128×17 meters, and the experimental results demonstrate the effectiveness and efficiency of proposed method. In conclusion, the proposed method is simple, effective and efficient and can be applied in a wide range of applications such as large scale road surface diagnose.
Physics experiment is a basic course in the colleges of science and technology. This course can cultivate students' ability by using experimental methods to discover, analyse and solve problems. At the same time, they can cultivate students' rigorous scientific thinking and innovative ability. In order to improve the efficiency of classroom teaching, promote their independent learning ability, we have introduced the flipped classroom concept into the teaching process, and carried out a deep reform of the original teaching mode. Herein, we discussed the existing problems of the current college physics experiment teaching mode, and the application of the flipped classroom mode in teaching process.
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