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[Introduction] Since the power line has the characteristics of long transmission distance and a complex spatial environment, the UAV LiDAR point cloud technology can completely and efficiently obtain the geometric information of the power line and its surrounding spatial objects, and the existing supervised extraction and unsupervised extraction methods are deficient in point cloud data extraction in a large range of complex environments, according to the spatial environment characteristics of the main network and distribution network line point cloud data, a rapid extraction method of point cloud power line is proposed based on projection line characteristics and region growing algorithm. [Method] Firstly, in view of the characteristics that the overhead lines of the main network were usually higher than the surrounding spatial objects, the power lines were roughly extracted by the elevation histogram threshold method. Then, considering the characteristics that the vegetation canopy was higher than the distribution network line in the distribution network area, the KNN data points of the roughly extracted power line point cloud were obtained, and the point cloud was projected on the horizontal plane, and whether the point cloud was a power line point cloud was judged by the linear measurement of the point cloud. [Result] According to the existence of missing power line point clouds, all the power line point cloud clusters are obtained through a region growing mode, and on this basis, the catenary formula of each power line point cloud cluster is calculated through the catenary formula, and the point cloud with a fitting distance less than the threshold is merged as the same power line point cloud. [Conclusion] The proposed method aims at the problem of rapid power line extraction in inspection applications and overcomes the problem of power line point cloud missing and vegetation impact in the process of power line extraction, so this method can achieve power line point cloud extraction with high efficiency and accuracy.

Objective: To investigate the effect of superchilling combined with modified atmosphere packaging (MAP) on the quality indicators of truffle during storage. Methods: Truffle samples were stored at −(4.4 ± 0.2) ℃ under normal atmosphere (control) and 40% O2 + 60% CO2 atmosphere (group A), and quality changes during storage were determined. Discriminant models were established using principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA). Results: Each quality index showed different trends under the two different storage atmospheres. Truffle was preserved significantly better in group A than the control group; the water loss and decay rate were effectively reduced in group A. On the 20th day of storage, the moisture content, decay rate and mass loss rate of group A were 63.62%, 6.94% and 1.02%, respectively; moisture content was significantly higher than control group (P < 0.05), and decay rate and mass loss rate were lower than control group, respectively (P < 0.05). Truffle quality was maintained better in group A than the control group, in terms of maintaining textural characteristics such as hardness and elasticity and delaying the decline in the contents of polysaccharides, total polyphenols, total flavonoids and crude protein and ferric ion reducing power. After 20 days of storage, the contents of polysaccharides, total polyphenols, total flavonoids and crude protein, and ferric ion reducing power were reduced by 27.94%, 32.51%, 16.18%, 68.58%, and 18.13%, respectively, which were lower than those in the control group. Correlation analysis and the developed discriminant models could effectively distinguish the quality differences of the samples under different treatments, indicating that physicochemical indexes influenced the quality of truffle during the storage period. OPLS-DA could also effectively differentiate the components of the truffle samples under different treatments. Conclusion: Superchilling combined with MAP can better preserve fresh truffle, and this study provides a theoretical basis for the development of new truffle preservation technologies.