The atmospheric boundary layer （ABL） is an important physical characteristic of the Earth＇s atmosphere. Compared with the typical ABL, the ABL in arid regions has distinct features and is formed by particular mecha...The atmospheric boundary layer （ABL） is an important physical characteristic of the Earth＇s atmosphere. Compared with the typical ABL, the ABL in arid regions has distinct features and is formed by particular mechanisms. In this paper, the depth of the diurnal and nocturnal ABLs and their related thermodynamic features of land surface processes, including net radiation, the ground-air temperature difference and sensible heat flux, under typical summer and winter conditions are discussed on the basis of comprehensive observations of the ABL and thermodynamic processes at the land surface carried out in the extreme arid zone of Dunhuang. The relationships of the ABL depth in the development and maintenance stages with these thermodynamic features are also investigated. The results show that the depth of the ABL is closely correlated with the thermodynamic features in both development and maintenance stages and more energy is consumed in the development stage. Further analysis indicates that wind velocity also affects ABL development, especially the development of a stable boundary layer in winter. Taken together, the analysis results indicate that extremely strong thermodynamic processes at the land surface are the main driving factor for the formation of a deep ABL in an arid region.展开更多
A 2nd order numerical manifold method(NMM) based method is developed to simulate the hydraulic fractures propagating process in rock or concrete. The proposed method uses a weak coupling technique to analyze the fluid...A 2nd order numerical manifold method(NMM) based method is developed to simulate the hydraulic fractures propagating process in rock or concrete. The proposed method uses a weak coupling technique to analyze the fluid phase and solid phase. To study the seepage behavior of the fluid phase, all the fractures in solid are identified by a block cutting algorithm and form a flow network. Then the hydraulic heads at crack ends are solved. To study the deformation and destruction of solid phase, the 2-order NMM and sub-region boundary element method are combined to solve the stress-strain field. Crack growth is controlled by the well-accepted criterion, including the tension criterion or Mohr-Coulomb criterion for the initialization of cracks and the maximum circumferential stress theory for crack propagation. Once the crack growth occurs, the seepage and deformation analysis will be resolved in the next simulation step. Such weak coupling analysis will continue until the structure becomes stable or is destructed. Five examples are used to verify the new method. The results demonstrate that the method can solve the SIFs at crack tip and fluid flow in crack network precisely, and the method is effective in simulating the hydraulic facture problem. Besides, the NMM shows great convenience and is of high accuracy in simulating the crack growth problem.展开更多
提出了柔性配电网(flexible distribution network,FDN)的安全域模型,并与传统配电网(traditional distribution network,TDN)对比分析。首先,介绍了FDN的概念与特点。其次,分析了FDN正常运行N-0和N-1下的安全约束。再次,提出了FDN的安...提出了柔性配电网(flexible distribution network,FDN)的安全域模型,并与传统配电网(traditional distribution network,TDN)对比分析。首先,介绍了FDN的概念与特点。其次,分析了FDN正常运行N-0和N-1下的安全约束。再次,提出了FDN的安全域模型以及安全边界方程。最后,通过单联络与多联络电缆网算例验证了本文方法的正确性,对FDN和TDN的N-0域、N-1域以及供电能力进行了对比研究。对比发现:1)FDN能扩大N-0/N-1域,提高正常运行情况下带负载的能力与N-1安全性;2)FDN达到不计及N-1和计及N-1下的最大供电能力工作点相比TDN多很多,使其在实际中更容易实现;3)FDN节点负荷能突破馈线容量限制,具有更大的局部带大负荷能力。同时,通过二维视图观察总结FDN安全域的形状特点及形成机理,并揭示其与柔性闭环特征的内在联系,最终从安全和高效角度分析得出多联络更适合发挥FDN作用的结论。展开更多
In this paper a mathematical model is built for a buried hot crude oil pipeline during shutdown, and an unstructured grid and polar coordinate grid are respectively applied to generating grids for the soil region and ...In this paper a mathematical model is built for a buried hot crude oil pipeline during shutdown, and an unstructured grid and polar coordinate grid are respectively applied to generating grids for the soil region and the three layers in the pipe （wax layer, pipe wall, and corrosion-inhibiting coating）. The governing equations are discretized using the finite volume method. The variations in temperatures of static oil and soil were investigated during pipeline shutdown in both summer and winter, in which some important parameters of the soil and crude oils of a Northeast pipeline are employed.展开更多
The active North China block consists of three second-order blocks: Ordos, North China Plain, and East Shandong-Huanghai Sea blocks. Two active tectonic zones, the Anyang-Heze- Linyi and Tangshan-Cixian zones, exist i...The active North China block consists of three second-order blocks: Ordos, North China Plain, and East Shandong-Huanghai Sea blocks. Two active tectonic zones, the Anyang-Heze- Linyi and Tangshan-Cixian zones, exist in the active North China Plain block and have separated the active block into 3 third-order active blocks, Taihangshan, Hebei-Shandong, and Henan-Huai blocks. The 3 third-order active blocks are characterized by their entire motion and are clearly different in their Cenozoic structures and deep structures. The active boundary tectonic zones between the third-order active blocks are less than those between the first- and second-order active blocks in their movement strength, extent, and seismic activity. The density of M ≥ 6 earthquakes in the boundary zones between active blocks is higher than that within the blocks by 9-22 times in the North China region, up to one order of magnitude on average. M ≥ 7 earthquakes occurred basically in the boundary zones between active blocks. The difference is not occasional, but reflects the nature of intraplate movement and the characteristics of strong seismic activity and is the powerful evidence for hypothesis of active blocks.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 40830957, 40805009)
文摘The atmospheric boundary layer （ABL） is an important physical characteristic of the Earth＇s atmosphere. Compared with the typical ABL, the ABL in arid regions has distinct features and is formed by particular mechanisms. In this paper, the depth of the diurnal and nocturnal ABLs and their related thermodynamic features of land surface processes, including net radiation, the ground-air temperature difference and sensible heat flux, under typical summer and winter conditions are discussed on the basis of comprehensive observations of the ABL and thermodynamic processes at the land surface carried out in the extreme arid zone of Dunhuang. The relationships of the ABL depth in the development and maintenance stages with these thermodynamic features are also investigated. The results show that the depth of the ABL is closely correlated with the thermodynamic features in both development and maintenance stages and more energy is consumed in the development stage. Further analysis indicates that wind velocity also affects ABL development, especially the development of a stable boundary layer in winter. Taken together, the analysis results indicate that extremely strong thermodynamic processes at the land surface are the main driving factor for the formation of a deep ABL in an arid region.
基金supported by the National Natural Science Foundation of China(Grant Nos.51439005&51209235)the National Basic Research Program of China("973"Project)(Grant Nos.2013CB035904,2013CB-036406)
文摘A 2nd order numerical manifold method(NMM) based method is developed to simulate the hydraulic fractures propagating process in rock or concrete. The proposed method uses a weak coupling technique to analyze the fluid phase and solid phase. To study the seepage behavior of the fluid phase, all the fractures in solid are identified by a block cutting algorithm and form a flow network. Then the hydraulic heads at crack ends are solved. To study the deformation and destruction of solid phase, the 2-order NMM and sub-region boundary element method are combined to solve the stress-strain field. Crack growth is controlled by the well-accepted criterion, including the tension criterion or Mohr-Coulomb criterion for the initialization of cracks and the maximum circumferential stress theory for crack propagation. Once the crack growth occurs, the seepage and deformation analysis will be resolved in the next simulation step. Such weak coupling analysis will continue until the structure becomes stable or is destructed. Five examples are used to verify the new method. The results demonstrate that the method can solve the SIFs at crack tip and fluid flow in crack network precisely, and the method is effective in simulating the hydraulic facture problem. Besides, the NMM shows great convenience and is of high accuracy in simulating the crack growth problem.
文摘提出了柔性配电网(flexible distribution network,FDN)的安全域模型,并与传统配电网(traditional distribution network,TDN)对比分析。首先,介绍了FDN的概念与特点。其次,分析了FDN正常运行N-0和N-1下的安全约束。再次,提出了FDN的安全域模型以及安全边界方程。最后,通过单联络与多联络电缆网算例验证了本文方法的正确性,对FDN和TDN的N-0域、N-1域以及供电能力进行了对比研究。对比发现:1)FDN能扩大N-0/N-1域,提高正常运行情况下带负载的能力与N-1安全性;2)FDN达到不计及N-1和计及N-1下的最大供电能力工作点相比TDN多很多,使其在实际中更容易实现;3)FDN节点负荷能突破馈线容量限制,具有更大的局部带大负荷能力。同时,通过二维视图观察总结FDN安全域的形状特点及形成机理,并揭示其与柔性闭环特征的内在联系,最终从安全和高效角度分析得出多联络更适合发挥FDN作用的结论。
基金supported by National High-tech R&D Program of China (No. 2006AA09Z357)the National Science Foundation of China (No. 50876114, No. 10602043)+1 种基金the Program for New Century Excellent Talents in University (NCET-07-0843) and SRF for ROCS, SEMsupported by the State Key Laboratory of Multiphase Flow in Power Engineering (Xi'an Jiaotong University)
文摘In this paper a mathematical model is built for a buried hot crude oil pipeline during shutdown, and an unstructured grid and polar coordinate grid are respectively applied to generating grids for the soil region and the three layers in the pipe （wax layer, pipe wall, and corrosion-inhibiting coating）. The governing equations are discretized using the finite volume method. The variations in temperatures of static oil and soil were investigated during pipeline shutdown in both summer and winter, in which some important parameters of the soil and crude oils of a Northeast pipeline are employed.
文摘The active North China block consists of three second-order blocks: Ordos, North China Plain, and East Shandong-Huanghai Sea blocks. Two active tectonic zones, the Anyang-Heze- Linyi and Tangshan-Cixian zones, exist in the active North China Plain block and have separated the active block into 3 third-order active blocks, Taihangshan, Hebei-Shandong, and Henan-Huai blocks. The 3 third-order active blocks are characterized by their entire motion and are clearly different in their Cenozoic structures and deep structures. The active boundary tectonic zones between the third-order active blocks are less than those between the first- and second-order active blocks in their movement strength, extent, and seismic activity. The density of M ≥ 6 earthquakes in the boundary zones between active blocks is higher than that within the blocks by 9-22 times in the North China region, up to one order of magnitude on average. M ≥ 7 earthquakes occurred basically in the boundary zones between active blocks. The difference is not occasional, but reflects the nature of intraplate movement and the characteristics of strong seismic activity and is the powerful evidence for hypothesis of active blocks.
