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Characterization of alpine meadow surface crack and its correlation with root-soil properties

Journal of Arid Land 2024年第6期16卷 834-851页

作者： WU Yuechen ZHU Haili ZHANG Yu ZHANG Hailong LIU Guosong LIU Yabin LI Guorong HU Xiasong School of Geological Engineering Qinghai UniversityXining 810016China Key Laboratory of the Cenozoic Resources and Environment on the North Rim of the Qinghai-Tibet Plateau Xining 810016China Qinghai Provincial Transportation Planning and Design Research Institute Co.Ltd. Xining 810002China

Quantifying surface cracks in alpine meadows is a prerequisite and a key aspect in the study of grassland crack development.crack characterization indices are crucial for the quantitative characterization of complex cracks,serving as vital factors in assessing the degree of cracking and the development morphology.So far,research on evaluating the degree of grassland degradation through crack characterization indices is rare,especially the quantitative analysis of the development of surface cracks in alpine meadows is relatively scarce.Therefore,based on the phenomenon of surface cracking during the degradation of alpine meadows in some regions of the Qinghai-Tibet Plateau,we selected the alpine meadow in the Huangcheng Mongolian Township,Menyuan Hui Autonomous County,Qinghai Province,China as the study area,used unmanned aerial vehicle(UAV)sensing technology to acquire low-altitude images of alpine meadow surface cracks at different degrees of degradation(light,medium,and heavy degradation),and analyzed the representative metrics characterizing the degree of crack development by interpreting the crack length,length density,branch angle,and burrow(rat hole)distribution density and combining them with in situ crack width and depth measurements.Finally,the correlations between the crack characterization indices and the soil and root parameters of sample plots at different degrees of degradation in the study area were analyzed using the grey relation analysis.The results revealed that with the increase of degradation,the physical and chemical properties of soil and the mechanical properties of root-soil composite changed significantly,the vegetation coverage reduced,and the root system aggregated in the surface layer of alpine meadow.As the degree of degradation increased,the fracture morphology developed from"linear"to"dendritic",and eventually to a complex and irregular"polygonal"pattern.The crack length,width,depth,and length density were identified as the crack characterization indices via analysis of variance.Th

关键词： alpine meadow grassland degradation grassland cracks crack characterization index crack morphology root length density grey relation analysis

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Study of material removal behavior on R-plane of sapphire during ultra-precision machining based on modified slip-fracture model

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Nanotechnology and Precision Engineering 2020年第3期3卷 141-155页

作者： Suk Bum Kwon Aditya Nagaraj Hae-Sung Yoon Sangkee Min Department of Mechanical Engineering University of Wisconsin-Madison1513 University AvenueMadisonWI 53706United States of America School of Aerospace and Mechanical Engineering Korea Aerospace University76 Hanggongdaehak-roDeogyang-guGoyang-siGyeonggi-do 10540Republic of Korea

In this paper, the modified slip/fracture activation model has been used in order to understand the mechanism of ductile-brittle transition on the R-plane of sapphire during ultra-precision machining by reflecting direction of resultant force. Anisotropic characteristics of crack morphology and ductility of machining depending on cutting direction were explained in detail with modified fracture cleavage and plastic deformation parameters. Through the analysis, it was concluded that crack morphologies were mainly determined by the interaction of multiple fracture systems activated while, critical depth of cut was determined by the dominant plastic deformation parameter. In addition to this, by using proportionality relationship between magnitude of resultant force and depth of cut in the ductile region, an empirical model for critical depth of cut was developed.

关键词： Ductile-brittle transition crack morphology Single crystal sapphire Deformation mechanism Orthogonal cutting Ultra-precision machining

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