Expansive soil is sensitive to dry and wet environment change. And the volume deformation and inflation pressure of expansive soil may induce to cause the deformation failure of roadbed or many other adverse effects. ...Expansive soil is sensitive to dry and wet environment change. And the volume deformation and inflation pressure of expansive soil may induce to cause the deformation failure of roadbed or many other adverse effects. Aimed at a high-speed railway engineering practice in the newly built Yun-Gui high-speed railway expansive soil section in China, indoor vibration test on a full-scaled new cutting subgrade model is carried out. Based on the established track-subgrade-foundation of expansive soil system dynamic model test platform, dynamic behavior of new cutting subgrade structure under train loads coupling with extreme service environment(dry, raining, and groundwater level rising) is analyzed comparatively. The results show that the subgrade dynamic response is significantly influenced by service conditions and the dynamic response of subgrade gradually becomes stable with the increasing vibration times under various service environment conditions. The vertical dynamic soil stress is related with the depth in an approximate exponential function, and the curves of vertical dynamic soil stress present a "Z" shape distribution along transverse distance. The peak value of dynamic soil stress appears below the rail, and it increases more obviously near the roadbed surface. However, the peak value of dynamic soil stress is little affected outside 5.0 m of center line. The vibration velocity and acceleration are in a quadratic curve with an increase in depth, and the raining and groundwater level rising increase both the vibration velocity and the acceleration. The vertical deformations at different depths are differently affected by service environment in roadbed. The deformation of roadbed increases sharply when the water gets in the foundation of expansive soil, and more than 60% of the total deformation of roadbed occurs in expansive soil foundation. The laid waterproofing and drainage structure layer, which weakens the dynamic stress and improves the track regularity, presents a positive effect on the control deformation of roadbed surface. An improved empirical formula is then proposed to predict the dynamic stress of ballasted tracks subgrade of expansive soil.展开更多
Early human embryonic development remains mysterious due to drastic species divergences between humans and othermammalian models and limited accessibility to human embryo samples. Recent studies from my laboratory and...Early human embryonic development remains mysterious due to drastic species divergences between humans and othermammalian models and limited accessibility to human embryo samples. Recent studies from my laboratory and others haveshown that under suitable culture conditions human pluripotent stem cells ( hPSCs) can undergo intricate morphogenetic eventsand self-organize to form patterned human embryo-like structures in vitro. These synthetic human embryonic tissueshold great promises for advancing human embryology and reproductive medicine. In this talk,I will describe a hPSC-based,synthetic 3D model of human post-implantation development that recapitulates key developmental landmarks successively,including pro-amniotic cavity formation,amniotic ectoderm-epiblast patterning,primordial germ cell specification,and developmentof the primitive streak with controlled anteroposterior polarity ( Fig.1) . We further show that the amniotic ectoderm,as the first lineage that segregates from the epiblast upon implantation of the human embryo,functions as a signaling centerto trigger primitive streak development in the epiblast. Together,our research has developed a powerful synthetic embryologicalmodel and provided new understandings of previously inaccessible but critical embryogenic events in human development.展开更多
The development of the socialist market economy demands the furtherintensification of the reform of the management operating system (MOS)of the state-owned assets, the strengthening of the efficiency in the man-agemen...The development of the socialist market economy demands the furtherintensification of the reform of the management operating system (MOS)of the state-owned assets, the strengthening of the efficiency in the man-agement of state-owned assets,and the improvement of the operating bene-展开更多
基金Projects(51478484,51308551,51678571)supported by the National Natural Science Foundation of ChinaProject(2016zzts063)supported by Fundamental Research Funds for the Central Universities,China
文摘Expansive soil is sensitive to dry and wet environment change. And the volume deformation and inflation pressure of expansive soil may induce to cause the deformation failure of roadbed or many other adverse effects. Aimed at a high-speed railway engineering practice in the newly built Yun-Gui high-speed railway expansive soil section in China, indoor vibration test on a full-scaled new cutting subgrade model is carried out. Based on the established track-subgrade-foundation of expansive soil system dynamic model test platform, dynamic behavior of new cutting subgrade structure under train loads coupling with extreme service environment(dry, raining, and groundwater level rising) is analyzed comparatively. The results show that the subgrade dynamic response is significantly influenced by service conditions and the dynamic response of subgrade gradually becomes stable with the increasing vibration times under various service environment conditions. The vertical dynamic soil stress is related with the depth in an approximate exponential function, and the curves of vertical dynamic soil stress present a "Z" shape distribution along transverse distance. The peak value of dynamic soil stress appears below the rail, and it increases more obviously near the roadbed surface. However, the peak value of dynamic soil stress is little affected outside 5.0 m of center line. The vibration velocity and acceleration are in a quadratic curve with an increase in depth, and the raining and groundwater level rising increase both the vibration velocity and the acceleration. The vertical deformations at different depths are differently affected by service environment in roadbed. The deformation of roadbed increases sharply when the water gets in the foundation of expansive soil, and more than 60% of the total deformation of roadbed occurs in expansive soil foundation. The laid waterproofing and drainage structure layer, which weakens the dynamic stress and improves the track regularity, presents a positive effect on the control deformation of roadbed surface. An improved empirical formula is then proposed to predict the dynamic stress of ballasted tracks subgrade of expansive soil.
基金supported by the National Science Foundation ( CMMI 1129611 and CBET 1149401)the National Institutes of Health ( R21 HL114011 and R21 EB017078)+3 种基金the American Heart Association ( 12SDG12180025)the Department of Mechanical Engineering at the University of Michigan,Ann ArborThe Lurie Nanofabrication Facility at the University of Michigan,a member of the National Nanotechnology Infrastructure Network ( NNIN)funded by the National Science Foundation,is acknowledged for support in microfabrication
文摘Early human embryonic development remains mysterious due to drastic species divergences between humans and othermammalian models and limited accessibility to human embryo samples. Recent studies from my laboratory and others haveshown that under suitable culture conditions human pluripotent stem cells ( hPSCs) can undergo intricate morphogenetic eventsand self-organize to form patterned human embryo-like structures in vitro. These synthetic human embryonic tissueshold great promises for advancing human embryology and reproductive medicine. In this talk,I will describe a hPSC-based,synthetic 3D model of human post-implantation development that recapitulates key developmental landmarks successively,including pro-amniotic cavity formation,amniotic ectoderm-epiblast patterning,primordial germ cell specification,and developmentof the primitive streak with controlled anteroposterior polarity ( Fig.1) . We further show that the amniotic ectoderm,as the first lineage that segregates from the epiblast upon implantation of the human embryo,functions as a signaling centerto trigger primitive streak development in the epiblast. Together,our research has developed a powerful synthetic embryologicalmodel and provided new understandings of previously inaccessible but critical embryogenic events in human development.
文摘The development of the socialist market economy demands the furtherintensification of the reform of the management operating system (MOS)of the state-owned assets, the strengthening of the efficiency in the man-agement of state-owned assets,and the improvement of the operating bene-
