滑坡预警预报是滑坡研究的热点和难点。速度倒数模型的简捷性和有效性使之成为广泛使用的临滑预报模型。滑坡变形加速开始点(Onset of Acceleration)直接影响到速度倒数模型的预报精度。本文基于经济学领域广泛使用的指数移动平均线,提...滑坡预警预报是滑坡研究的热点和难点。速度倒数模型的简捷性和有效性使之成为广泛使用的临滑预报模型。滑坡变形加速开始点(Onset of Acceleration)直接影响到速度倒数模型的预报精度。本文基于经济学领域广泛使用的指数移动平均线,提出了准确识别滑坡变形加速开始点的方法:(1)将滑坡速度绝对值化;(2)定义趋势变化指数ω,利用滑动时间窗口法,识别滑坡加速趋势区;(3)对加速趋势区进行速度倒数线性拟合,根据线性拟合的相关性系数,识别滑坡加速变形开始点。在此基础上,以云南省区布嘎渐变型滑坡为例,对模型识别出的OOA点准确性进行了验证,结果表明:利用本文提出的方法,可准确识别渐变型滑坡的OOA点,利用识别的OOA点对后续数据进行线性回归,其相关性系数在0.8以上,预测误差在4 d以下,显示出较好的预测结果。展开更多
Hydraulic stimulation technology is widely employed to enhance the permeability of geothermal reservoirs.Nevertheless,accurately predicting hydraulic fracture propagation in complex geological conditions remains chall...Hydraulic stimulation technology is widely employed to enhance the permeability of geothermal reservoirs.Nevertheless,accurately predicting hydraulic fracture propagation in complex geological conditions remains challenging,thereby hindering the effective utilization of existing natural fractures.In this study,a phase field model was developed utilizing the finite element method to examine the influence of fluid presence,stress conditions,and natural fractures on the initiation and propagation of hydraulic fractures.The model employs Biot's poroelasticity theory to establish the coupling between the displacement field and the fluid field,while the phase field theory is applied to simulate fracture behavior.The results show that whenσ_(x0)/σ_(y0)<3 or qf<20 kg/(m^(3)·s),the presence of natural fractures can alter the original propagation direction of hydraulic fractures.Conversely,in the absence of these conditions,the propagation path of natural fractures is predominantly influenced by the initial stress field.Furthermore,based on the analysis of breakdown pressure and damage area,the optimal intersection angle between natural fractures and hydraulic fractures is determined to range from 45°to 60°.Finally,once a dominant channel forms,initiating and propagating hydraulic fractures in other directions becomes increasingly difficult,even in highly fractured areas.This method tackles the challenges of initiating and propagating hydraulic fractures in complex geological conditions,providing a theoretical basis for optimizing Enhanced Geothermal System(EGS)projects.展开更多
Objectives: To identify the etiology and source after recognition of diarrhea outbreak is associated with drinking water in suburb of Chengdu. Methods: Both unmatched case control and retrospective cohort study were c...Objectives: To identify the etiology and source after recognition of diarrhea outbreak is associated with drinking water in suburb of Chengdu. Methods: Both unmatched case control and retrospective cohort study were conducted. 131 targets including 56 suspected patients were recruited for case control study, while 463 residents were selected for cohort study. Stool, water and environmental samples were collected for laboratory testing. Results: The proportion of case exposed to well water was 86% in case group compared with 51% in the controls during the epidemic period (OR = 6.14, P P P E. coli and Enterotoxigenic E. coli was positive in stool and river samples. Conclusions: This outbreak of diarrhea might be caused by several mixed opportunistic pathogens in well water contaminated from the river water.展开更多
文摘滑坡预警预报是滑坡研究的热点和难点。速度倒数模型的简捷性和有效性使之成为广泛使用的临滑预报模型。滑坡变形加速开始点(Onset of Acceleration)直接影响到速度倒数模型的预报精度。本文基于经济学领域广泛使用的指数移动平均线,提出了准确识别滑坡变形加速开始点的方法:(1)将滑坡速度绝对值化;(2)定义趋势变化指数ω,利用滑动时间窗口法,识别滑坡加速趋势区;(3)对加速趋势区进行速度倒数线性拟合,根据线性拟合的相关性系数,识别滑坡加速变形开始点。在此基础上,以云南省区布嘎渐变型滑坡为例,对模型识别出的OOA点准确性进行了验证,结果表明:利用本文提出的方法,可准确识别渐变型滑坡的OOA点,利用识别的OOA点对后续数据进行线性回归,其相关性系数在0.8以上,预测误差在4 d以下,显示出较好的预测结果。
基金supported by the National Key Research and Development Program(2021YFB150740401)National Natural Science Foundation of China(42202336)the CAS Pioneer Hundred Talents Program in China(Y826031C01)。
文摘Hydraulic stimulation technology is widely employed to enhance the permeability of geothermal reservoirs.Nevertheless,accurately predicting hydraulic fracture propagation in complex geological conditions remains challenging,thereby hindering the effective utilization of existing natural fractures.In this study,a phase field model was developed utilizing the finite element method to examine the influence of fluid presence,stress conditions,and natural fractures on the initiation and propagation of hydraulic fractures.The model employs Biot's poroelasticity theory to establish the coupling between the displacement field and the fluid field,while the phase field theory is applied to simulate fracture behavior.The results show that whenσ_(x0)/σ_(y0)<3 or qf<20 kg/(m^(3)·s),the presence of natural fractures can alter the original propagation direction of hydraulic fractures.Conversely,in the absence of these conditions,the propagation path of natural fractures is predominantly influenced by the initial stress field.Furthermore,based on the analysis of breakdown pressure and damage area,the optimal intersection angle between natural fractures and hydraulic fractures is determined to range from 45°to 60°.Finally,once a dominant channel forms,initiating and propagating hydraulic fractures in other directions becomes increasingly difficult,even in highly fractured areas.This method tackles the challenges of initiating and propagating hydraulic fractures in complex geological conditions,providing a theoretical basis for optimizing Enhanced Geothermal System(EGS)projects.
文摘Objectives: To identify the etiology and source after recognition of diarrhea outbreak is associated with drinking water in suburb of Chengdu. Methods: Both unmatched case control and retrospective cohort study were conducted. 131 targets including 56 suspected patients were recruited for case control study, while 463 residents were selected for cohort study. Stool, water and environmental samples were collected for laboratory testing. Results: The proportion of case exposed to well water was 86% in case group compared with 51% in the controls during the epidemic period (OR = 6.14, P P P E. coli and Enterotoxigenic E. coli was positive in stool and river samples. Conclusions: This outbreak of diarrhea might be caused by several mixed opportunistic pathogens in well water contaminated from the river water.
