Araneiforms are spider-like ground patterns that are widespread in the southern polar regions of Mars.A gas erosion process driven by the seasonal sublimation of CO_(2)ice was proposed as an explanation for their form...Araneiforms are spider-like ground patterns that are widespread in the southern polar regions of Mars.A gas erosion process driven by the seasonal sublimation of CO_(2)ice was proposed as an explanation for their formation,which cannot occur on Earth due to the high climatic temperature.In this study,we propose an alternative mechanism that attrib-utes the araneiform formation to the erosion of upwelling salt water from the subsurface,relying on the identification of the first terrestrial analog found in a playa of the Qaidam Basin on the northern Tibetan Plateau.Morphological analysis indicates that the structures in the Qaidam Basin have fractal features comparable to araneiforms on Mars.A numerical model is developed to investigate the araneiform formation driven by the water-diffusion mechanism.The simulation res-ults indicate that the water-diffusion process,under varying ground conditions,may be responsible for the diverse aranei-form morphologies observed on both Earth and Mars.Our numerical simulations also demonstrate that the orientations of the saltwater diffusion networks are controlled by pre-existing polygonal cracks,which is consistent with observations of araneiforms on Mars and Earth.Our study thus suggests that a saltwater-related origin of the araneiform is possible and has significant implications for water searches on Mars.展开更多
Luonan Basin, formed during Neo\|tectonic movements, is one of the small block basins in East Qinling Mountain. Three faults, Tieluzi Fault, Dajing\|Guojiayuan Fault and Beisi Fault bound it. The west part of the basi...Luonan Basin, formed during Neo\|tectonic movements, is one of the small block basins in East Qinling Mountain. Three faults, Tieluzi Fault, Dajing\|Guojiayuan Fault and Beisi Fault bound it. The west part of the basin is higher than the east part. The elevation, usually more than 1100meters in the west, decreases gradually to less than 800meters in the east. The Cenozoic deposit in Luonan Basin is thin in the west part and becomes increasingly thick towards the east part. The total thickness of both the Eogene and the Neogene is only more than 100meters at Dajing. At Duishan, a place close to Luonan county town, it is about 400meters, and at Gucheng, it becomes nearly 1750meters. The strata crop out in the west part of the basin, usually the Eogene and the Neogene, are older than those in the east part which are usually the Quaternary deposits. The pattern of the Cenozoic deposits in Luonan Basin is similar to that in Shangzhou Basin (Li Kaoshe, personal communication), a basin locating just to the south of Luonan Basin.展开更多
The effects of the different landforms of the cutting leeward on the aerodynamic performance of high-speed trains were analyzed based on the three-dimensional, steady, and incompressible Navier-Stokes equation and k-e...The effects of the different landforms of the cutting leeward on the aerodynamic performance of high-speed trains were analyzed based on the three-dimensional, steady, and incompressible Navier-Stokes equation and k-e double-equation turbulent model. Results show that aerodynamic forces increase with the cutting leeward slope decreasing. The maximum adding value of lateral force, lift force, and overturning moment are 147%, 44.3%, and 107%, respectively, when the slope varies from 0.67 to -0.67, and the changes in the cutting leeward landform have more effects on the aerodynamic performance when the train is running in the line No. 2 than in the line No. 1. The aerodynamic forces, except the resistance force, sharply increase with the slope depth decreasing. By comparing the circumstance of the cutting depth H=-8 m with that of H=8 m, the resistance force, lateral force, lift force, and overturning moment increase by 26.0%, 251%, 67.3% and 177%, respectively. With the wind angle increasing, the resistance force is nonmonotonic, whereas other forces continuously rise. Under three special landforms, the changes in the law of aerodynamic forces with the wind angle are almost similar to one another.展开更多
Located on the western of Sichuan, the east border of Tibet plateau, Xianshuihe fault is a significant strong earthquake zone. From Huiyuansi pull\|apart basin in Qianning, Xianshuihe fault can be divided two segments...Located on the western of Sichuan, the east border of Tibet plateau, Xianshuihe fault is a significant strong earthquake zone. From Huiyuansi pull\|apart basin in Qianning, Xianshuihe fault can be divided two segments\|NW section and SE section: the construction of the former is single and a main fault; the construction of the latter is complex and composed by three parallel faults, its main fault is named as Selaha—Kangding fault, which distributes along Jinlongsi, Sehala, Mugecuo and Kangding. Yalahe fault, located at the NE direction of the main fault, and Zeduotang fault, located at the SW direction of the main fault, are all secondary faults, which are 9～13km away from the main fault. At the south of Kangding, the segment of Xianshuihe fault is a single main section, called as Moxi fault. On the basis of recent researching results, this paper mainly discusses the slip rate and recurrence interval of strong earthquake of the SE segment (Qianning—Kangding) on Xianshuihe.展开更多
Neotectonic movement controls the configuration of landform, and the landform controls the hydraulic conditions. The latter is the dynamie factor of karst development. 1. The general configuration of landform in China...Neotectonic movement controls the configuration of landform, and the landform controls the hydraulic conditions. The latter is the dynamie factor of karst development. 1. The general configuration of landform in China The mscroscopic topography of this count(?) is that the elevation of western part is higher than that of eastern part, which forms a three(?) landform,展开更多
The development of tropical karst in Guilin could be dated back to middle Triassic, i.e. up to 240 million years, and the incipient karst landform was formed from the middle Triassic to the early Jurassic, a period wi...The development of tropical karst in Guilin could be dated back to middle Triassic, i.e. up to 240 million years, and the incipient karst landform was formed from the middle Triassic to the early Jurassic, a period with intensive karstification. Later, the karst in the area has experienced three major periods, that is, the weak period from the middle Jurassic to the late Cretaceous; the intensive period in the Tertiary which was significant to the formation of the old Li River; and the third period lasts the Quaternary period which has completed the typical tropical karst landform. Some ideas about the effect of paleo lake water to the formation of the tropical karst and the ages of caves on different levels in Guilin have been put forward.展开更多
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB41000000)the Fundamental Research Funds for the Central Universities(WK2080000144)。
文摘Araneiforms are spider-like ground patterns that are widespread in the southern polar regions of Mars.A gas erosion process driven by the seasonal sublimation of CO_(2)ice was proposed as an explanation for their formation,which cannot occur on Earth due to the high climatic temperature.In this study,we propose an alternative mechanism that attrib-utes the araneiform formation to the erosion of upwelling salt water from the subsurface,relying on the identification of the first terrestrial analog found in a playa of the Qaidam Basin on the northern Tibetan Plateau.Morphological analysis indicates that the structures in the Qaidam Basin have fractal features comparable to araneiforms on Mars.A numerical model is developed to investigate the araneiform formation driven by the water-diffusion mechanism.The simulation res-ults indicate that the water-diffusion process,under varying ground conditions,may be responsible for the diverse aranei-form morphologies observed on both Earth and Mars.Our numerical simulations also demonstrate that the orientations of the saltwater diffusion networks are controlled by pre-existing polygonal cracks,which is consistent with observations of araneiforms on Mars and Earth.Our study thus suggests that a saltwater-related origin of the araneiform is possible and has significant implications for water searches on Mars.
文摘Luonan Basin, formed during Neo\|tectonic movements, is one of the small block basins in East Qinling Mountain. Three faults, Tieluzi Fault, Dajing\|Guojiayuan Fault and Beisi Fault bound it. The west part of the basin is higher than the east part. The elevation, usually more than 1100meters in the west, decreases gradually to less than 800meters in the east. The Cenozoic deposit in Luonan Basin is thin in the west part and becomes increasingly thick towards the east part. The total thickness of both the Eogene and the Neogene is only more than 100meters at Dajing. At Duishan, a place close to Luonan county town, it is about 400meters, and at Gucheng, it becomes nearly 1750meters. The strata crop out in the west part of the basin, usually the Eogene and the Neogene, are older than those in the east part which are usually the Quaternary deposits. The pattern of the Cenozoic deposits in Luonan Basin is similar to that in Shangzhou Basin (Li Kaoshe, personal communication), a basin locating just to the south of Luonan Basin.
基金Project(U1134203) supported by the National Natural Science Foundation of ChinaProject(132014) supported by Fok Ying Tong Education Foundation,ChinaProject(2011G006) supported by the Technological Research and Development Program of the Ministry of Railways,China
文摘The effects of the different landforms of the cutting leeward on the aerodynamic performance of high-speed trains were analyzed based on the three-dimensional, steady, and incompressible Navier-Stokes equation and k-e double-equation turbulent model. Results show that aerodynamic forces increase with the cutting leeward slope decreasing. The maximum adding value of lateral force, lift force, and overturning moment are 147%, 44.3%, and 107%, respectively, when the slope varies from 0.67 to -0.67, and the changes in the cutting leeward landform have more effects on the aerodynamic performance when the train is running in the line No. 2 than in the line No. 1. The aerodynamic forces, except the resistance force, sharply increase with the slope depth decreasing. By comparing the circumstance of the cutting depth H=-8 m with that of H=8 m, the resistance force, lateral force, lift force, and overturning moment increase by 26.0%, 251%, 67.3% and 177%, respectively. With the wind angle increasing, the resistance force is nonmonotonic, whereas other forces continuously rise. Under three special landforms, the changes in the law of aerodynamic forces with the wind angle are almost similar to one another.
文摘Located on the western of Sichuan, the east border of Tibet plateau, Xianshuihe fault is a significant strong earthquake zone. From Huiyuansi pull\|apart basin in Qianning, Xianshuihe fault can be divided two segments\|NW section and SE section: the construction of the former is single and a main fault; the construction of the latter is complex and composed by three parallel faults, its main fault is named as Selaha—Kangding fault, which distributes along Jinlongsi, Sehala, Mugecuo and Kangding. Yalahe fault, located at the NE direction of the main fault, and Zeduotang fault, located at the SW direction of the main fault, are all secondary faults, which are 9～13km away from the main fault. At the south of Kangding, the segment of Xianshuihe fault is a single main section, called as Moxi fault. On the basis of recent researching results, this paper mainly discusses the slip rate and recurrence interval of strong earthquake of the SE segment (Qianning—Kangding) on Xianshuihe.
文摘Neotectonic movement controls the configuration of landform, and the landform controls the hydraulic conditions. The latter is the dynamie factor of karst development. 1. The general configuration of landform in China The mscroscopic topography of this count(?) is that the elevation of western part is higher than that of eastern part, which forms a three(?) landform,
文摘The development of tropical karst in Guilin could be dated back to middle Triassic, i.e. up to 240 million years, and the incipient karst landform was formed from the middle Triassic to the early Jurassic, a period with intensive karstification. Later, the karst in the area has experienced three major periods, that is, the weak period from the middle Jurassic to the late Cretaceous; the intensive period in the Tertiary which was significant to the formation of the old Li River; and the third period lasts the Quaternary period which has completed the typical tropical karst landform. Some ideas about the effect of paleo lake water to the formation of the tropical karst and the ages of caves on different levels in Guilin have been put forward.
