Curvature analysis of triangulated surfaces in structural geology

This paper addresses the problem of characterizing the shape of a geological surface on the basis of its principal curvatures. The surface is assumed to be modeled as a set of adjacent triangles defined by the location of their vertices and a method is proposed for estimating numerically the principal curvatures at the vertices of the triangles using a local C² interpolant. Also shown is how principal curvatures can be useful for studying the deformation of a geological surface (with application to 3D balanced unfolding), and analyzing the folding or faulting of the interface between two adjacent layers.     

Variations in spring leaf phenology and leaf freezing damage of common woody species in China北大核心CSCD

Freezing damage results in the dehydration of plant cells and reduces the photosynthetic capacity of plants, which causes significant losses to ecology and economy. Over the past 40 years, global warming has reduced the frequency and intensity of frost events while bringing forward the spring phenology of plants, increasing the exposure of their leaves and flowers to harsh cold temperatures. Therefore, the dual effects of climate warming should be considered in order to accurately assess the changes of plant freezing damage. To date, there is no systematic analysis of plant freezing damage in different climatic regions of China. Based on phenological observation records from the China Phenological Observation Network, leaf frost damage of four common woody plants (Ulmus pumila, Robinia pseudoacacia, Salix babylonica, Fraxinus chinensis) in the spring over the past 40 years was calculated, and the spatio-temporal patterns were analyzed. We also investigated the change in the occurrence time of maximum frost damage (TMFD) and its relationship with plant phenology. The results show that: 1) Most species presented an overall trend towards an earlier leaf unfolding date, and the advancing trend was significant and greater than 1 d/a in about 60% of the regions (P<0.05). 2) The TMFD occurred earlier in 72.22%-83.03% of the regions, which was closely related to plants' earlier leaf unfolding date. The TMFD of all species advanced the most (8.3 days) in the temperate climate zone, followed by the warm temperate, subtropical, plateau, and cold temperate zones. 3) The leaves of U. pumila, R. pseudoacacia and S. babylonica suffered more freezing damage in the spring, and the most significant freezing damage was mainly found in the north of 50°N region and part of the west of the Qinghai-Tibet Plateau. In comparison, the leaves of F. chinensis suffered less frost damage due to later leaf unfolding date and stronger leaf frost resistance. With regard to interannual variations, the average freezing damage of U. pumila, R. pseudoacacia and S. babylonica increased significantly (P<0.05), but that of F. chinensis did not change obviously. In addition, the freezing damage of U. pumila and S. babylonica increased the most in the cold temperate zone, while that of R. pseudoacacia increased in about 10% of the regions in the plateau climate zone, and 3%-6% of the regions in the cold temperate, temperate, and warm temperate climate zones. The freezing damage of F. chinensis merely increased in the warm temperate zone. The results of this study can provide a reference for assessing the risk of plant freezing damage accurately and help develop regional-specific response and adaptation strategies to climate change. © 2023, Editorial office of PROGRESS IN GEOGRAPHY. All rights reserved.     

A Velocity Dealiasing Scheme for C-band Weather Radar Systems简

A dealiasing algorithm for radar radial velocity observed by C-band Doppler radars is presented as an extension of an existing S-band dealiasing algorithm. This has operational significance in that many portable and many commercial broadcast radars, as well as approximately one half of the Chinese weather radar network （CINRAD）, are C-band radars. With a wavelength of about 5 cm, the Nyquist interval of C-band radars is just about one half that of S-band radars （wavelength of about 10 cm） and thus has more velocity folding. The proposed algorithm includes seven modules to remove noisy data, find the starting radials, dealias velocities, and apply least squares error checking in both the radial and azimuth directions. The proposed velocity dealiasing method was applied to one widespread rain case and three strong convective cases from radars operating in China. It was found that, on average, 92.95% of the aliased radial velocity data could be correctly de-aliased by the algorithm, resulting in 96.65% of the data being valid.     

多普勒天气雷达风场退模糊方法的研究

文章提出了对多普勒天气雷达的风场信息进行预处理的“K-邻域频数法”,该方法物理统计意义比较明确,能够有效地处理风场信息中的“噪声”问题。在此基础上,设计了单径向的速度扩展算法,并提出了“双径向-双切向”的方法, 其效果与美国WSR-88D。NSSL和FSL的算法相当。该文还设计了一个界面十分友好的人机交互方法,可以达到约90%以上的速度扩展正确率,是对传统的人机交互方法的极大改进。     

铜离子对海参精氨酸激酶活力与结构的影响

精氨酸激酶(Arginine kinase,EC2.7.3.3)是无脊椎动物能量代谢所必需的重要的酶.海参精氨酸激酶是一种特殊的双亚基精氨酸激酶.本文研究了在二价铜离子作用下,海参精氨酸激酶催化活性与结构的变化.结果表明,一定浓度的铜离子,可以抑制精氨酸激酶的活力,并引起酶二级结构与三级结构的变化,引起疏水面暴露,并导...