目的:利用医学影像构建个性化主动脉弓模型,对主动脉弓血流动力学特性进行较为系统的分析。方法:通过心脏三维图像得到包括小血管的较为完整的主动脉弓几何模型,采用Carreau黏度模型和其他控制方程建立主动脉弓血流动力学模型,通过有限...目的:利用医学影像构建个性化主动脉弓模型,对主动脉弓血流动力学特性进行较为系统的分析。方法:通过心脏三维图像得到包括小血管的较为完整的主动脉弓几何模型,采用Carreau黏度模型和其他控制方程建立主动脉弓血流动力学模型,通过有限元数值求解得到主动脉弓的血流动力学数值结果,并进行血流动力学特性分析。结果:降主动脉出口与入口流量之比为94.32%,其余小血管出口流量之和仅占5.68%;在大血管中,血流的压强并不是均匀分布的,不同点的压强之差在收缩期可能达到4.54 mm Hg(1 mm Hg=133.322 Pa);主动脉弓中剪切力最大处位于几个小血管分叉的上方;在收缩期的下降期主动脉弓大血管中涡流也非常明显。结论:该研究有助于加深对主动脉弓血流动力学特性的理解,对研究动脉血管疾病有一定的启发。展开更多
Snowfall in the Tianshan Mountains in China is frequent during winter;thus,avalanches have become a severe issue in snow-covered areas.Accumulation and metamorphosis,as well as hydrothermal exchanges with the environm...Snowfall in the Tianshan Mountains in China is frequent during winter;thus,avalanches have become a severe issue in snow-covered areas.Accumulation and metamorphosis,as well as hydrothermal exchanges with the environment,considerably affect the stability of snow on slopes.Therefore,a hydrothermal model of snow cover and its underlying surfaces must be developed on the basis of meteorological data to predict and help manage avalanches.This study adopted the conceptual model of snow as a porous medium and quantitatively analysed its internal physical processes on the basis of the thermal exchanges amongst its components.The effects of local meteorological factors on snow structure and the redistribution of energy and mass inside the snow cover in the Tianshan Mountains were simulated.Simulation results showed that deformation as a result of overlying snow and sublimation of snow cover at the bottom is the main cause of density variation in the vertical profile of snow cover.Temperature drives water movement in snow.The low-density area of the bottom snow is the result of temperature gradient.The simulation results of the long-term snow internal mass distribution obtained by the method established in this study are highly consistent with the actual observed trend of variation.Such consistency indicates an accurate simulation of the physical characteristics of snow cover in small and microscale metamorphism in the Tianshan Mountains during the stable period.展开更多
文摘目的:利用医学影像构建个性化主动脉弓模型,对主动脉弓血流动力学特性进行较为系统的分析。方法:通过心脏三维图像得到包括小血管的较为完整的主动脉弓几何模型,采用Carreau黏度模型和其他控制方程建立主动脉弓血流动力学模型,通过有限元数值求解得到主动脉弓的血流动力学数值结果,并进行血流动力学特性分析。结果:降主动脉出口与入口流量之比为94.32%,其余小血管出口流量之和仅占5.68%;在大血管中,血流的压强并不是均匀分布的,不同点的压强之差在收缩期可能达到4.54 mm Hg(1 mm Hg=133.322 Pa);主动脉弓中剪切力最大处位于几个小血管分叉的上方;在收缩期的下降期主动脉弓大血管中涡流也非常明显。结论:该研究有助于加深对主动脉弓血流动力学特性的理解,对研究动脉血管疾病有一定的启发。
基金supported by the 13th Five-year Informatization Plan of the Chinese Academy of Sciences,Grant No.XXH13506 and XXH13505-220Data sharing fundamental program for Construction of the National Science Technology Infrastructure Platform(Grant No.Y719H71006)。
文摘Snowfall in the Tianshan Mountains in China is frequent during winter;thus,avalanches have become a severe issue in snow-covered areas.Accumulation and metamorphosis,as well as hydrothermal exchanges with the environment,considerably affect the stability of snow on slopes.Therefore,a hydrothermal model of snow cover and its underlying surfaces must be developed on the basis of meteorological data to predict and help manage avalanches.This study adopted the conceptual model of snow as a porous medium and quantitatively analysed its internal physical processes on the basis of the thermal exchanges amongst its components.The effects of local meteorological factors on snow structure and the redistribution of energy and mass inside the snow cover in the Tianshan Mountains were simulated.Simulation results showed that deformation as a result of overlying snow and sublimation of snow cover at the bottom is the main cause of density variation in the vertical profile of snow cover.Temperature drives water movement in snow.The low-density area of the bottom snow is the result of temperature gradient.The simulation results of the long-term snow internal mass distribution obtained by the method established in this study are highly consistent with the actual observed trend of variation.Such consistency indicates an accurate simulation of the physical characteristics of snow cover in small and microscale metamorphism in the Tianshan Mountains during the stable period.
