Carotid or cerebral artery stenosis resulting in low perfusion is a major cause of ischemic stroke.Understanding the unique hemodynamic features in each patient undergoing a stroke-in-progress（SIP） and the correlati...Carotid or cerebral artery stenosis resulting in low perfusion is a major cause of ischemic stroke.Understanding the unique hemodynamic features in each patient undergoing a stroke-in-progress（SIP） and the correlation between progression and cerebral blood flow（CBF） status would help in the diagnosis and treatment of individual patients.We used xenonenhanced CT（Xe-CT） to examine cerebral perfusion in patients with or without SIP（30 patients/group）,recruited from October 2009 to October 2010.Only SIP patients with unilateral stenosis in the internal or middle cerebral artery were recruited.The occurrence of watershed infarction was higher in the SIP group than in the non-SIP group（P ＆lt;0.05）.In the SIP group,larger hypoperfused areas were found around the lesions than in the non-SIP group.In the SIP group,the CBF values in the ipsilateral areas were significantly lower than those in corresponding regions on the contralateral side.CBF values in the contralateral hemisphere were significantly lower in the SIP group than in the non-SIP group.In SIP patients,infarctions were surrounded by larger hypoperfused areas than in non-SIP patients.These larger hypoperfused areas may result in pathological damage to the brain that is responsible for the progression of stroke.展开更多
Numerical study about vortex-induced vibration （V/V） related to a flexible riser model in consideration of internal flow progressing inside has been performed. The main objective of this work is to investigate the c...Numerical study about vortex-induced vibration （V/V） related to a flexible riser model in consideration of internal flow progressing inside has been performed. The main objective of this work is to investigate the coupled fluid-structure interaction （FSI） taking place between tensioned riser model, external shear current and upward-progressing internal flow （from ocean bottom to surface）. A CAE technology behind the current research which combines structural software with the CFD technology has been proposed. According to the result from dynamic analysis, it has been found that the existence of upward-progressing internal flow does play an important role in determining the vibration mode （/dominant frequency）, vibration intensity and the magnitude of instantaneous vibration amplitude, when the velocity ratio of internal flow against external current is relatively high. As a rule, the larger the velocity of intemal flow is, the more it contributes to the dynamic vibration response of the flexible riser model. In addition, multi-modal vibration phenomenon has been widely observed, for asymmetric curvature along the riser span emerges in the case of external shear current being imposed.展开更多
Landslides occurring in sensitive clay often result in widespread destruction,posing a significant risk to human lives and property due to the substantial decrease in undrained shear strength during deformation.Assess...Landslides occurring in sensitive clay often result in widespread destruction,posing a significant risk to human lives and property due to the substantial decrease in undrained shear strength during deformation.Assessing the consequences of these landslides is challenging and necessitates robust numerical methods to comprehensively investigate their failure mechanisms.While studies have extensively explored upward progressive landslides in sensitive clays,understanding downward progressive cases remains limited.In this study,we utilised the nodal integration-based particle finite element method(NPFEM)with a nonlinear strain-softening model to analyse downward progressive landslides in sensitive clay on elongated slopes,induced by surcharge loads near the crest.We focused on elucidating the underlying failure mechanisms and evaluating the effects of different soil parameters and strainsoftening characteristics.The simulation results revealed the typical pattern for downward landslides,which typically start with a localised failure in proximity to the surcharge loads,followed by a combination of different types of failure mechanisms,including single flow slides,translational progressive landslides,progressive flow slides,and spread failures.Additionally,inclined shear bands occur within spread failures,often adopting distinctive ploughing patterns characterised by triangular shapes.The sensitive clay thickness at the base,the clay strength gradient,the sensitivity,and the softening rate significantly influence the failure mechanisms and the extent of diffused displacement.Remarkably,some of these effects mirror those observed in upward progressive landslides,underscoring the interconnectedness of these phenomena.This study contributes valuable insights into the complex dynamics of sensitive clay landslides,shedding light on the intricate interplay of factors governing their behaviour and progression.展开更多
基金supported by grants from Health Department of Jilin Province,China(2008P007)Science and Technology Department of Jilin Province,China(200705148)
文摘Carotid or cerebral artery stenosis resulting in low perfusion is a major cause of ischemic stroke.Understanding the unique hemodynamic features in each patient undergoing a stroke-in-progress（SIP） and the correlation between progression and cerebral blood flow（CBF） status would help in the diagnosis and treatment of individual patients.We used xenonenhanced CT（Xe-CT） to examine cerebral perfusion in patients with or without SIP（30 patients/group）,recruited from October 2009 to October 2010.Only SIP patients with unilateral stenosis in the internal or middle cerebral artery were recruited.The occurrence of watershed infarction was higher in the SIP group than in the non-SIP group（P ＆lt;0.05）.In the SIP group,larger hypoperfused areas were found around the lesions than in the non-SIP group.In the SIP group,the CBF values in the ipsilateral areas were significantly lower than those in corresponding regions on the contralateral side.CBF values in the contralateral hemisphere were significantly lower in the SIP group than in the non-SIP group.In SIP patients,infarctions were surrounded by larger hypoperfused areas than in non-SIP patients.These larger hypoperfused areas may result in pathological damage to the brain that is responsible for the progression of stroke.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41106077, 51109185 and 51109186)Zhejiang Provincial Natural Science Foundation of China (Grant Nos. R5110036 and Y5110071)+2 种基金Science Research Program of Science Technology Department of Zhejiang Province (Grant No. 2011C24005)Korea Research Foundation (Grant No. KRF-2008-D00556)Scientific Research Foundation of Zhejiang Ocean University
文摘Numerical study about vortex-induced vibration （V/V） related to a flexible riser model in consideration of internal flow progressing inside has been performed. The main objective of this work is to investigate the coupled fluid-structure interaction （FSI） taking place between tensioned riser model, external shear current and upward-progressing internal flow （from ocean bottom to surface）. A CAE technology behind the current research which combines structural software with the CFD technology has been proposed. According to the result from dynamic analysis, it has been found that the existence of upward-progressing internal flow does play an important role in determining the vibration mode （/dominant frequency）, vibration intensity and the magnitude of instantaneous vibration amplitude, when the velocity ratio of internal flow against external current is relatively high. As a rule, the larger the velocity of intemal flow is, the more it contributes to the dynamic vibration response of the flexible riser model. In addition, multi-modal vibration phenomenon has been widely observed, for asymmetric curvature along the riser span emerges in the case of external shear current being imposed.
基金support provided by the UK Engineering and Physical Sciences Research Council(EP/V012169/1).
文摘Landslides occurring in sensitive clay often result in widespread destruction,posing a significant risk to human lives and property due to the substantial decrease in undrained shear strength during deformation.Assessing the consequences of these landslides is challenging and necessitates robust numerical methods to comprehensively investigate their failure mechanisms.While studies have extensively explored upward progressive landslides in sensitive clays,understanding downward progressive cases remains limited.In this study,we utilised the nodal integration-based particle finite element method(NPFEM)with a nonlinear strain-softening model to analyse downward progressive landslides in sensitive clay on elongated slopes,induced by surcharge loads near the crest.We focused on elucidating the underlying failure mechanisms and evaluating the effects of different soil parameters and strainsoftening characteristics.The simulation results revealed the typical pattern for downward landslides,which typically start with a localised failure in proximity to the surcharge loads,followed by a combination of different types of failure mechanisms,including single flow slides,translational progressive landslides,progressive flow slides,and spread failures.Additionally,inclined shear bands occur within spread failures,often adopting distinctive ploughing patterns characterised by triangular shapes.The sensitive clay thickness at the base,the clay strength gradient,the sensitivity,and the softening rate significantly influence the failure mechanisms and the extent of diffused displacement.Remarkably,some of these effects mirror those observed in upward progressive landslides,underscoring the interconnectedness of these phenomena.This study contributes valuable insights into the complex dynamics of sensitive clay landslides,shedding light on the intricate interplay of factors governing their behaviour and progression.
