In recent years, flash flood disasters have occurred frequently in southwest China due to the increased frequency of extreme climate events. To solve this problem, great efforts have been made in studying the process ...In recent years, flash flood disasters have occurred frequently in southwest China due to the increased frequency of extreme climate events. To solve this problem, great efforts have been made in studying the process of flash flood. However, little attention was paid on bearing body of hazard, the clusters of buildings. Thus the real disaster mechanism of flash flood remains unclear.Accordingly, based on the experiments of artificial flash floods in a conceptual solid model, this paper focuses on the flood-impacted inundation characteristics of the building clusters at different locations of the gully model, in order to obtain a better understanding of the disaster process and the interaction between the flash floods and building clusters. The results showed that, in a typical smallscale flash flood gully with hot and dry climate, 1)clusters of buildings on an alluvial fan could reduce about 35% of the flooding area by blocking the diffusion of the flood to the depression areas, and could also promote the deposition in lower reaches of the river channel by blocking the overbank flow from going back into the channel, making the width-depth ratio of the channel larger. 2) The flash flood rates of disaster and hazard on the alluvial fan are generally higher than that of the inner gully. For the inner gully,buildings located on the beaches along the lower river and the transitional areas of the straight channel and channel bends can easily be affected because of their lower elevations. For the alluvial fan, buildings nearby the meanders suffer the greatest impacts because of bank collapsing and flooding. 3) The safe vertical distance from a building to the river channel is 13 m for the buildings in the inner gully under extreme floods. Below this threshold, the smaller the vertical distance is, the greater the risk exposure is. For the buildings on the alluvial fan, especially for the buildings near the concave bank of the top rush point,the horizontal distance is more important, and the safe value is 80 m under extreme floods.展开更多
This paper presents a field based method to deal with the displacement of building cluster, which is driven by the street widening. The compress of street boundary results in the force to push the building moving insi...This paper presents a field based method to deal with the displacement of building cluster, which is driven by the street widening. The compress of street boundary results in the force to push the building moving inside and the force propagation is a decay process. To describe the phenomenon above, the field theory is introduced with the representation model of isoline. On the basis of the skeleton of Delaunay triangulation, the displacement field is built in which the propagation force is related to the adjacency degree with respect to the street boundary. The study offers the computation of displacement direction and offset distance for the building displacement. The vector operation is performed on the basis of grade and other field concepts.展开更多
Ab initio total energy calculations are used to simulate the building of equiatomic solid APballoys (A=Li, Na, K) with A4Pb4 clusters which are particularly stable in the gas phase. Theeight clusters per unit cell wer...Ab initio total energy calculations are used to simulate the building of equiatomic solid APballoys (A=Li, Na, K) with A4Pb4 clusters which are particularly stable in the gas phase. Theeight clusters per unit cell were drawn together by shrinking the cell in stages, and allowingfull atomic relaxation at each stage. Charged Pb4 tetrahedral units dominate the structuraland electronic properties, and these units are remarkably robust and insensitive to their alkalienvironment. The stability of the Pb4 units diminishes as we progress from K to Li and lead totheir absence in the LiPb alloy in accordance with experiment. The distance between Pb4 unitsseems to be the critical factor responsible for the structural trends, which is determined by theatomic size of the alkali.展开更多
基金supported by the Specific Research of China Institute of Water Resources and Hydropower Research (Grant Nos. Fangji 1240)Chinese Ministry of Water Resources (Grant Nos. 201301058 and 20131059)the Basic Research Fund for Central Public Research Institutes (Grant No. CKSF2015010/TB)
文摘In recent years, flash flood disasters have occurred frequently in southwest China due to the increased frequency of extreme climate events. To solve this problem, great efforts have been made in studying the process of flash flood. However, little attention was paid on bearing body of hazard, the clusters of buildings. Thus the real disaster mechanism of flash flood remains unclear.Accordingly, based on the experiments of artificial flash floods in a conceptual solid model, this paper focuses on the flood-impacted inundation characteristics of the building clusters at different locations of the gully model, in order to obtain a better understanding of the disaster process and the interaction between the flash floods and building clusters. The results showed that, in a typical smallscale flash flood gully with hot and dry climate, 1)clusters of buildings on an alluvial fan could reduce about 35% of the flooding area by blocking the diffusion of the flood to the depression areas, and could also promote the deposition in lower reaches of the river channel by blocking the overbank flow from going back into the channel, making the width-depth ratio of the channel larger. 2) The flash flood rates of disaster and hazard on the alluvial fan are generally higher than that of the inner gully. For the inner gully,buildings located on the beaches along the lower river and the transitional areas of the straight channel and channel bends can easily be affected because of their lower elevations. For the alluvial fan, buildings nearby the meanders suffer the greatest impacts because of bank collapsing and flooding. 3) The safe vertical distance from a building to the river channel is 13 m for the buildings in the inner gully under extreme floods. Below this threshold, the smaller the vertical distance is, the greater the risk exposure is. For the buildings on the alluvial fan, especially for the buildings near the concave bank of the top rush point,the horizontal distance is more important, and the safe value is 80 m under extreme floods.
文摘This paper presents a field based method to deal with the displacement of building cluster, which is driven by the street widening. The compress of street boundary results in the force to push the building moving inside and the force propagation is a decay process. To describe the phenomenon above, the field theory is introduced with the representation model of isoline. On the basis of the skeleton of Delaunay triangulation, the displacement field is built in which the propagation force is related to the adjacency degree with respect to the street boundary. The study offers the computation of displacement direction and offset distance for the building displacement. The vector operation is performed on the basis of grade and other field concepts.
文摘Ab initio total energy calculations are used to simulate the building of equiatomic solid APballoys (A=Li, Na, K) with A4Pb4 clusters which are particularly stable in the gas phase. Theeight clusters per unit cell were drawn together by shrinking the cell in stages, and allowingfull atomic relaxation at each stage. Charged Pb4 tetrahedral units dominate the structuraland electronic properties, and these units are remarkably robust and insensitive to their alkalienvironment. The stability of the Pb4 units diminishes as we progress from K to Li and lead totheir absence in the LiPb alloy in accordance with experiment. The distance between Pb4 unitsseems to be the critical factor responsible for the structural trends, which is determined by theatomic size of the alkali.
