Contorted hexabenzocoronene(c-HBC)and its derivatives,as an important class of polycyclic aromatic hydrocarbons(PAHs)with non-planar configurations,exhibit broad application prospects in organic electronics,photovoltaic devices,and supramolecular self-assembly due to their unique structural and optoelectronic properties.This review summarizes the bottom-up solution-phase synthetic strategies for c-HBC and its derivatives,primarily including synthetic routes based on the Barton-Kellogg reactions,the Ramirez-Corey-Fuchs reactions,and the covalent self-assembly(CSA)strategy.In addition,this review also summarizes synthetic strategies for preparing nitrogen-and boron-doped c-HBC.Through a systematic overview of different synthetic pathways,this work aims to provide theoretical guidance and experimental references for the precise construction of c-HBC and its derivatives.
Coastal soils in the Yangtze River Delta are often characterized by compaction,limited permeability,and salinization,and these constrains hinder the healthy growth and landscape performance of high-ornamental-value plants such as cherry blossoms under rapid urbanization.This study selected the Beidao green space in the Lingang New Area of Shanghai as the experiment site and used the Cerasus×yedoensis'Somei-Yoshino'as the test species.Two treatments were established:a'Chenshan formula soil'treatment(CS,volumetric ratio:50%stones+20%wood chips+15%peat+15%original soils)and a control using the original soil(CK).Soil physicochemical properties and morphological-physiological indicators of cherry blossom roots and above-ground parts were systematically measured to evaluate the effects of soil improvement on both growth performance and landscape quality.The results showed that:(1)Compared with CK,CS significantly deceased soil bulk density,increased porosity,raised the contents of organic carbon,total nitrogen,available phosphorus,and available potassium,and enhanced cation exchange capacity,accompanied by a reduction in soil alkalinity.(2)Under CS,the root density of cherry blossoms was extremely significantly higher than that of CK,while the above-ground parts exhibited improved petal morphology and a significant increase in chlorophyll content.Overall,CS improved the physicochemical properties of coastal soils,promoted root development and above-ground growth,and enhanced the landscape quality of'Somei-Yoshino'cherry blossoms.These findings provide a feasible technical pathway and scientific reference for soil improvement in similar coastal landscape greening projects.
The particle swarm optimization(PSO)algorithm is widely used in electromagnetic inversion due to its simplicity,ease of implementation,and strong global search capability.However,its fitness evaluation step requires solving numerous forward electromagnetic problems,which entails extremely high computational costs with traditional methods.To address this,this paper constructs a branch-decoding forward problem-solving structure based on multi-scale U-Net,enhancing the fitness of PSO algorithm for electromagnetic parameter inversion.Experimental results demonstrate that this method can effectively improve the iteration efficiency of PSO algorithm while maintaining its inversion accuracy.
For the small target segmentation task of building curtain wall sealant cracks,this paper introduces dilated convolution and attention mechanism,and proposes an improved U-Net(DEU-Net)based on context information enhancement,exploring the impact of context information and attention mechanism on segmentation accuracy.Experiments are conducted based on a self-built sealant crack dataset.The results show that DEU-Net performs better in metrics such as mean pixel accuracy(mPA)and mean intersection over union(mIoU),with complete and accurate segmentation results.This study verifies that dilated convolution and attention mechanism can effectively integrate multi-scale context and enhance the performance of small target segmentation models.
Classroom teaching evaluation is a crucial tool for improving teaching and promoting teachers'professional development.However,traditional classroom observation and evaluation still rely heavily on manual recording in terms of"evidence collection-quantification and statistics-visualization presentation",making it difficult to consistently depict key behavioral characteristics during the classroom process.To this end,this paper proposes a classroom teaching process evaluation method based on teachers'visual attention,which relies solely on fixed classroom cameras to capture classroom videos.It constructs a head detection and pose estimation model,projects the teacher's head orientation into a two-dimensional gaze cone,and performs hit determination.Quantifiable indicators are calculated at three levels:individual students,classroom areas,and teaching behaviors,and visual evidence such as heat maps,regional attention timelines,and behavior timelines are generated.Based on the traditional classroom teaching observation scale,this paper also designs an extended evaluation form that incorporates visual attention evidence,supporting"processual,data-driven,and traceable"classroom teaching evaluation and diagnostic improvement.At the same time,it discusses the applicable boundaries and responsible use points of head orientation as a proxy evidence of visual attention,providing an extensible methodological reference for classroom teaching evaluation reform and teacher professional development.
