In this paper,based on the common soil erosion model,the Three-River Headwaters region was select for study object. GIS methods are applied to conduct Semi-quantitative assessment for different types of soil erosion,a...In this paper,based on the common soil erosion model,the Three-River Headwaters region was select for study object. GIS methods are applied to conduct Semi-quantitative assessment for different types of soil erosion,and some results are concluded. The water erosion occurs in High Mountain and extra-high mountain of Yushu,Nangqian,Banma and Jiuzhi County in the southeast and south of the Three-River Headwaters region. The degree of erosion is prone to topography,precipitation,river and human activity. The freeze-thaw erosion mainly distributes in the northwest of the Three-River Headwaters region. The area of middle and above middle erosion degree accounts for roughly 50%.展开更多
Assume that the Tonglu Canal would be widened and deepened in which a water lock is constructed atthe river side, and made open to the sea side. The canal's planned control dimensions are determined, and the erosi...Assume that the Tonglu Canal would be widened and deepened in which a water lock is constructed atthe river side, and made open to the sea side. The canal's planned control dimensions are determined, and the erosionand siltation characteristics along the river (totally 81. 8 km) are analyzed by the numerical calculation of one-dimen-sional unsteady flow and the relative standards. According to the data of the evolution, hydrology and sediment inthe Xiaomiaohong Waterway, it is found reasonable to select the channel near the Xingang Gate as the second sea-entering approach. This paper is helpful in planning and designing the approach.展开更多
The arc erosion under medium direct currents in the argon flow was tested on tungsten-copper（W-Cu） contacts which were processed by hot extrusion and heat treatment. The scanning electron microscopy（SEM） and trans...The arc erosion under medium direct currents in the argon flow was tested on tungsten-copper（W-Cu） contacts which were processed by hot extrusion and heat treatment. The scanning electron microscopy（SEM） and transmission electron microscopy（TEM） were used to study the microstructure of the W-Cu powders and compacts. The contact resistance, arcing energy, and arcing time were continuously measured by JF04C contact materials test system. Changes in tungsten-copper contact surface were observed by SEM. The test results showed that the arcing time and arcing energy all increase with current and voltage, but the changes of average contact resistance are more complicated. For a short arcing time, the average contact resistance decreases with increasing current due to the vaporization of Cu. However, for a longer arcing time, it slightly increases due to the formation of high resistant films, compound copper tungsten. The formation of compound copper tungsten was confirmed by the increased Rc kept in the range from 1.1 to 1.6 mΩ. The compound copper tungsten is first exposed with a tungsten and copper-rich surface, and then totally exposed due to evaporation of copper from the surface. At last a stabilized surface is created and the crystals decrease from 8 μm to 2 μm caused by the arc erosion.展开更多
Gully feature mapping is an indispensable prerequisite for the motioning and control of gully erosion which is a widespread natural hazard. The increasing availability of high-resolution Digital Elevation Model(DEM) a...Gully feature mapping is an indispensable prerequisite for the motioning and control of gully erosion which is a widespread natural hazard. The increasing availability of high-resolution Digital Elevation Model(DEM) and remote sensing imagery, combined with developed object-based methods enables automatic gully feature mapping. But still few studies have specifically focused on gully feature mapping on different scales. In this study, an object-based approach to two-level gully feature mapping, including gully-affected areas and bank gullies, was developed and tested on 1-m DEM and Worldview-3 imagery of a catchment in the Chinese Loess Plateau. The methodology includes a sequence of data preparation, image segmentation, metric calculation, and random forest based classification. The results of the two-level mapping were based on a random forest model after investigating the effects of feature selection and class-imbalance problem. Results show that the segmentation strategy adopted in this paper which considers the topographic information and optimal parameter combination can improve the segmentation results. The distribution of the gully-affected area is closely related to topographic information, however, the spectral features are more dominant for bank gully mapping. The highest overall accuracy of the gully-affected area mapping was 93.06% with four topographic features. The highest overall accuracy of bank gully mapping is 78.5% when all features are adopted. The proposed approach is a creditable option for hierarchical mapping of gully feature information, which is suitable for the application in hily Loess Plateau region.展开更多
The erosion risk below the dam of Er Tan project, which comes from the flood relief of the spillway and mid- dle outlet spillway, is analysed by risk analysis theory. According to the analysis results, it is imperativ...The erosion risk below the dam of Er Tan project, which comes from the flood relief of the spillway and mid- dle outlet spillway, is analysed by risk analysis theory. According to the analysis results, it is imperative that the stilling pool below the dam should be adopted to protect river bed from erosion. From the view of risk-protection and economy, the Er Tan project design scheme that adopted the stilling pool is coincident with safe and economical rules. It is efficient and scientific. The erosion risk analysis method used in the paper can be used in other projects. The results are certainly of reference value and great significance for engineering design.展开更多
文摘In this paper,based on the common soil erosion model,the Three-River Headwaters region was select for study object. GIS methods are applied to conduct Semi-quantitative assessment for different types of soil erosion,and some results are concluded. The water erosion occurs in High Mountain and extra-high mountain of Yushu,Nangqian,Banma and Jiuzhi County in the southeast and south of the Three-River Headwaters region. The degree of erosion is prone to topography,precipitation,river and human activity. The freeze-thaw erosion mainly distributes in the northwest of the Three-River Headwaters region. The area of middle and above middle erosion degree accounts for roughly 50%.
文摘Assume that the Tonglu Canal would be widened and deepened in which a water lock is constructed atthe river side, and made open to the sea side. The canal's planned control dimensions are determined, and the erosionand siltation characteristics along the river (totally 81. 8 km) are analyzed by the numerical calculation of one-dimen-sional unsteady flow and the relative standards. According to the data of the evolution, hydrology and sediment inthe Xiaomiaohong Waterway, it is found reasonable to select the channel near the Xingang Gate as the second sea-entering approach. This paper is helpful in planning and designing the approach.
文摘The arc erosion under medium direct currents in the argon flow was tested on tungsten-copper（W-Cu） contacts which were processed by hot extrusion and heat treatment. The scanning electron microscopy（SEM） and transmission electron microscopy（TEM） were used to study the microstructure of the W-Cu powders and compacts. The contact resistance, arcing energy, and arcing time were continuously measured by JF04C contact materials test system. Changes in tungsten-copper contact surface were observed by SEM. The test results showed that the arcing time and arcing energy all increase with current and voltage, but the changes of average contact resistance are more complicated. For a short arcing time, the average contact resistance decreases with increasing current due to the vaporization of Cu. However, for a longer arcing time, it slightly increases due to the formation of high resistant films, compound copper tungsten. The formation of compound copper tungsten was confirmed by the increased Rc kept in the range from 1.1 to 1.6 mΩ. The compound copper tungsten is first exposed with a tungsten and copper-rich surface, and then totally exposed due to evaporation of copper from the surface. At last a stabilized surface is created and the crystals decrease from 8 μm to 2 μm caused by the arc erosion.
基金Under the auspices of Priority Academic Program Development of Jiangsu Higher Education Institutions,National Natural Science Foundation of China(No.41271438,41471316,41401440,41671389)
文摘Gully feature mapping is an indispensable prerequisite for the motioning and control of gully erosion which is a widespread natural hazard. The increasing availability of high-resolution Digital Elevation Model(DEM) and remote sensing imagery, combined with developed object-based methods enables automatic gully feature mapping. But still few studies have specifically focused on gully feature mapping on different scales. In this study, an object-based approach to two-level gully feature mapping, including gully-affected areas and bank gullies, was developed and tested on 1-m DEM and Worldview-3 imagery of a catchment in the Chinese Loess Plateau. The methodology includes a sequence of data preparation, image segmentation, metric calculation, and random forest based classification. The results of the two-level mapping were based on a random forest model after investigating the effects of feature selection and class-imbalance problem. Results show that the segmentation strategy adopted in this paper which considers the topographic information and optimal parameter combination can improve the segmentation results. The distribution of the gully-affected area is closely related to topographic information, however, the spectral features are more dominant for bank gully mapping. The highest overall accuracy of the gully-affected area mapping was 93.06% with four topographic features. The highest overall accuracy of bank gully mapping is 78.5% when all features are adopted. The proposed approach is a creditable option for hierarchical mapping of gully feature information, which is suitable for the application in hily Loess Plateau region.
文摘The erosion risk below the dam of Er Tan project, which comes from the flood relief of the spillway and mid- dle outlet spillway, is analysed by risk analysis theory. According to the analysis results, it is imperative that the stilling pool below the dam should be adopted to protect river bed from erosion. From the view of risk-protection and economy, the Er Tan project design scheme that adopted the stilling pool is coincident with safe and economical rules. It is efficient and scientific. The erosion risk analysis method used in the paper can be used in other projects. The results are certainly of reference value and great significance for engineering design.
