The phase-field method is used to study the free dendritic crystal growth under forced convection with hypergravity,the hypergravity term is introduced into the liquid-phase momentum equation to examine the dendritic ...The phase-field method is used to study the free dendritic crystal growth under forced convection with hypergravity,the hypergravity term is introduced into the liquid-phase momentum equation to examine the dendritic growth.The paper focuses on the morphology of dendrite growth as well as the tip radius of the upstream dendritic arm and the average growth velocity of dendrite tips under different hypergravity levels.The results show that the morphology of dendrite changes significantly under represent simulation conditions when the hypergravity reaches 35_(g0),the upstream dendritic arm will bifurcate and the horizontal dendrite arms gradually tilt upwards.This change is mainly caused by the hypergravity and flow changing the temperature field near the dendrite interface.In addition,before the morphology of the dendrite is significantly altered,the radius of the tip of the dendrite upstream arm becomes larger with the increase in hypergravity,and the average growth velocity will increase linearly with it.The morphology of dendritic growth under different hypergravity and the changes in the tip radius along with the average growth velocity of the upstream dendritic tip with hypergravity are given in this paper.Finally,the reasons for these phenomena are analyzed.展开更多
China’s urbanization has entered a mid-to-late phase,and is characterized by high-density urban engineering projects that form systems coupled to geotechnical environments.These systems exhibit significant vulnerabil...China’s urbanization has entered a mid-to-late phase,and is characterized by high-density urban engineering projects that form systems coupled to geotechnical environments.These systems exhibit significant vulnerability due to strong spatiotemporal coupling,which hampers sustainable urban development.Traditional approaches to urban engineering design,construction,and maintenance tend to focus on individual projects and lack the ability to comprehensively evaluate system-level sustainability.Thus,with current methods,it is difficult to optimize the renewal and operation of high-density urban engineering systems.In this study,the constituent elements and key features of high-density urban engineering systems are discussed,and urban engineering system sustainability evaluation indicators are comprehensively reviewed.Viewed from perspectives of resilience,low-carbon development,and ecological impact,66 performance indicators describing urban engineering systems are selected.The decision-making trial and evaluation laboratory(DEMATEL)-based analytic network process(DANP)method and the entropy weight method(EWM)are utilized to calculate these indicators’subjective and objective weights,respectively.Furthermore,the coupling relationships between evaluation indicators are explored,aiding the construction of an urban engineering sustainability evaluation index system.Finally,empirical analysis is conducted across six megacities in China(Tianjin,Hangzhou,Shanghai,Wuhan,Chongqing,and Shenzhen)to validate the effectiveness of the evaluation indicators.The findings reveal significant imbalances in the sustainability of urban engineering systems in China.Accordingly,potential strategies and indicators for targeted enhancement of these systems are discussed.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.52588202)。
文摘The phase-field method is used to study the free dendritic crystal growth under forced convection with hypergravity,the hypergravity term is introduced into the liquid-phase momentum equation to examine the dendritic growth.The paper focuses on the morphology of dendrite growth as well as the tip radius of the upstream dendritic arm and the average growth velocity of dendrite tips under different hypergravity levels.The results show that the morphology of dendrite changes significantly under represent simulation conditions when the hypergravity reaches 35_(g0),the upstream dendritic arm will bifurcate and the horizontal dendrite arms gradually tilt upwards.This change is mainly caused by the hypergravity and flow changing the temperature field near the dendrite interface.In addition,before the morphology of the dendrite is significantly altered,the radius of the tip of the dendrite upstream arm becomes larger with the increase in hypergravity,and the average growth velocity will increase linearly with it.The morphology of dendritic growth under different hypergravity and the changes in the tip radius along with the average growth velocity of the upstream dendritic tip with hypergravity are given in this paper.Finally,the reasons for these phenomena are analyzed.
基金supported by the Fundamental Research Funds for the Central Universities(No.226-2024-00242)the Excellent Research Groups Project(No.52588202)the National Science Fund for Distinguished Young Scholars of China(No.52125803).
文摘China’s urbanization has entered a mid-to-late phase,and is characterized by high-density urban engineering projects that form systems coupled to geotechnical environments.These systems exhibit significant vulnerability due to strong spatiotemporal coupling,which hampers sustainable urban development.Traditional approaches to urban engineering design,construction,and maintenance tend to focus on individual projects and lack the ability to comprehensively evaluate system-level sustainability.Thus,with current methods,it is difficult to optimize the renewal and operation of high-density urban engineering systems.In this study,the constituent elements and key features of high-density urban engineering systems are discussed,and urban engineering system sustainability evaluation indicators are comprehensively reviewed.Viewed from perspectives of resilience,low-carbon development,and ecological impact,66 performance indicators describing urban engineering systems are selected.The decision-making trial and evaluation laboratory(DEMATEL)-based analytic network process(DANP)method and the entropy weight method(EWM)are utilized to calculate these indicators’subjective and objective weights,respectively.Furthermore,the coupling relationships between evaluation indicators are explored,aiding the construction of an urban engineering sustainability evaluation index system.Finally,empirical analysis is conducted across six megacities in China(Tianjin,Hangzhou,Shanghai,Wuhan,Chongqing,and Shenzhen)to validate the effectiveness of the evaluation indicators.The findings reveal significant imbalances in the sustainability of urban engineering systems in China.Accordingly,potential strategies and indicators for targeted enhancement of these systems are discussed.
