Structural defects such as joints or faults are inherent to almost any rock mass.In many situations those defects have a major impact on slope stability as they can control the possible failure mechanisms.Having a goo...Structural defects such as joints or faults are inherent to almost any rock mass.In many situations those defects have a major impact on slope stability as they can control the possible failure mechanisms.Having a good estimate of their strength then becomes crucial.The roughness of a structure is a major contributor to its strength through two different aspects,i.e.the morphology of the surface(or the shape)and the strength of the asperities(related to the strength of the rock).In the current state of practice,roughness is assessed through idealized descriptions(Patton strength criterion)or through empirical parameters(Barton JRC).In both cases,the multi-dimensionality of the roughness is ignored.In this study,we propose to take advantage of the latest developments in numerical techniques.With3D photogrammetry and/or laser mapping,practitioners have access to the real morphology of an exposed structure.The derived triangulated surface was introduced into the DEM(discrete element method)code PFC3D to create a synthetic rock joint.The interaction between particles on either side of the discontinuity was described by a smooth-joint model(SJM),hence suppressing the artificial roughness introduced by the particle discretization.Shear tests were then performed on the synthetic rock joint.A good correspondence between strengths predicted by the model and strengths derived from well-established techniques was obtained for thefirst time.Amongst the benefits of the methodology is the possibility offered by the model to be used in a quantitative way for shear strength estimates,to reproduce the progressive degradation of the asperities upon shearing and to analyze structures of different scales without introducing any empirical relation.展开更多
Background Cell source is one of the most important constructions for tissue engineered blood vessels(TEBV). As human adult vascular cells are limited by the replicative life spans and poor collagen secretion, stem ce...Background Cell source is one of the most important constructions for tissue engineered blood vessels(TEBV). As human adult vascular cells are limited by the replicative life spans and poor collagen secretion, stem cell has become a promising cell source. Hence, we investigated the differentiation of human induced pluripotent stem cells(hiPSC) into functional smooth-muscle-like cells(SMLCs) by embryoid bodies method and explored whether transforming growth factor-β1(TGF-β1) can promote the differentiation. Methods HiPSCs were cultured in smooth muscle cell medium with or without TGF-β1 after forming embryoid bodies. The cell morphology, cell characteristics and contractility were compared after 7 days of differentiation. Real-time PCR and Western blot were used to assess the mRNA and protein expression levels of α-SMA, Calponin, SM22α, Collagen I and Collagen III. Functional contraction study was performed using carbachol. Results HiPSC could successfully differentiate into cells that were similar to typical smooth muscle cells in morphology. The expression of α-SMA, Calponin and SM22α up-regulated after induction. TGF-β1 could further up-regulated α-SMA expression.Immunofluorescence images showed that more than 80% of the hiPSC-derived SMLCs by TGF-β1 stained with smooth muscle cell markers α-SMA, SMMHC, SM22α and Calponin. Analyses of expression in collagen showed that hiPSC-derived SMLCs exhibited higher levels of Collagen I and Collagen III after induction by TGF-β1. Conclusion The hiPSC could successfully differentiate into smooth-muscle-like cells using embryoid bodies method. TGF-β1 can promote the differentiation and enhance collagen synthesis[.S Chin J Cardiol 2019;20(1):44-53]展开更多
近年来,部分特高压换流变压器在运行中相继发生电弧短路故障并引发爆炸、起火事故,严重威胁直流系统安全稳定运行。充油设备故障冲击下的结构失效机制尚不明确,且缺乏成熟的数值计算方法,制约故障防爆技术的发展。基于此,该文提出一套...近年来,部分特高压换流变压器在运行中相继发生电弧短路故障并引发爆炸、起火事故,严重威胁直流系统安全稳定运行。充油设备故障冲击下的结构失效机制尚不明确,且缺乏成熟的数值计算方法,制约故障防爆技术的发展。基于此,该文提出一套适用于高能电弧故障冲击的结构失效仿真计算方法。首先,建立有限腔体内油中电弧能量持续注入的气泡动力学模型,准确描述故障气泡的脉动膨胀行为;其次,提出自适应有限元-光滑粒子流体动力学(finite element method-smoothed particle hydrodynamics,FEM-SPH)耦合方法,利用SPH粒子继承失效前的物理信息参与FEM计算;进行不同能量、不同位置的电弧故障仿真计算,获得换流变压器结构的薄弱区域及其破裂行为,复现了油箱结构失效行为。研究发现,油箱顶盖两侧及侧壁转角接缝位置容易发生应力集中现象。一旦结构出现裂缝,将在极短时间内沿着应力集中方向快速发展,最终导致壁面整体撕裂。可知,该方法揭示的结构失效行为可为改进变压器设计和提高设备安全性提供依据。展开更多
基金funding provided by the Swiss Federal Office for Water and Geology
文摘Structural defects such as joints or faults are inherent to almost any rock mass.In many situations those defects have a major impact on slope stability as they can control the possible failure mechanisms.Having a good estimate of their strength then becomes crucial.The roughness of a structure is a major contributor to its strength through two different aspects,i.e.the morphology of the surface(or the shape)and the strength of the asperities(related to the strength of the rock).In the current state of practice,roughness is assessed through idealized descriptions(Patton strength criterion)or through empirical parameters(Barton JRC).In both cases,the multi-dimensionality of the roughness is ignored.In this study,we propose to take advantage of the latest developments in numerical techniques.With3D photogrammetry and/or laser mapping,practitioners have access to the real morphology of an exposed structure.The derived triangulated surface was introduced into the DEM(discrete element method)code PFC3D to create a synthetic rock joint.The interaction between particles on either side of the discontinuity was described by a smooth-joint model(SJM),hence suppressing the artificial roughness introduced by the particle discretization.Shear tests were then performed on the synthetic rock joint.A good correspondence between strengths predicted by the model and strengths derived from well-established techniques was obtained for thefirst time.Amongst the benefits of the methodology is the possibility offered by the model to be used in a quantitative way for shear strength estimates,to reproduce the progressive degradation of the asperities upon shearing and to analyze structures of different scales without introducing any empirical relation.
基金supported by Science and Technology Planning Project of Guangdong Province,China(No.2016B070701007)
文摘Background Cell source is one of the most important constructions for tissue engineered blood vessels(TEBV). As human adult vascular cells are limited by the replicative life spans and poor collagen secretion, stem cell has become a promising cell source. Hence, we investigated the differentiation of human induced pluripotent stem cells(hiPSC) into functional smooth-muscle-like cells(SMLCs) by embryoid bodies method and explored whether transforming growth factor-β1(TGF-β1) can promote the differentiation. Methods HiPSCs were cultured in smooth muscle cell medium with or without TGF-β1 after forming embryoid bodies. The cell morphology, cell characteristics and contractility were compared after 7 days of differentiation. Real-time PCR and Western blot were used to assess the mRNA and protein expression levels of α-SMA, Calponin, SM22α, Collagen I and Collagen III. Functional contraction study was performed using carbachol. Results HiPSC could successfully differentiate into cells that were similar to typical smooth muscle cells in morphology. The expression of α-SMA, Calponin and SM22α up-regulated after induction. TGF-β1 could further up-regulated α-SMA expression.Immunofluorescence images showed that more than 80% of the hiPSC-derived SMLCs by TGF-β1 stained with smooth muscle cell markers α-SMA, SMMHC, SM22α and Calponin. Analyses of expression in collagen showed that hiPSC-derived SMLCs exhibited higher levels of Collagen I and Collagen III after induction by TGF-β1. Conclusion The hiPSC could successfully differentiate into smooth-muscle-like cells using embryoid bodies method. TGF-β1 can promote the differentiation and enhance collagen synthesis[.S Chin J Cardiol 2019;20(1):44-53]
文摘近年来,部分特高压换流变压器在运行中相继发生电弧短路故障并引发爆炸、起火事故,严重威胁直流系统安全稳定运行。充油设备故障冲击下的结构失效机制尚不明确,且缺乏成熟的数值计算方法,制约故障防爆技术的发展。基于此,该文提出一套适用于高能电弧故障冲击的结构失效仿真计算方法。首先,建立有限腔体内油中电弧能量持续注入的气泡动力学模型,准确描述故障气泡的脉动膨胀行为;其次,提出自适应有限元-光滑粒子流体动力学(finite element method-smoothed particle hydrodynamics,FEM-SPH)耦合方法,利用SPH粒子继承失效前的物理信息参与FEM计算;进行不同能量、不同位置的电弧故障仿真计算,获得换流变压器结构的薄弱区域及其破裂行为,复现了油箱结构失效行为。研究发现,油箱顶盖两侧及侧壁转角接缝位置容易发生应力集中现象。一旦结构出现裂缝,将在极短时间内沿着应力集中方向快速发展,最终导致壁面整体撕裂。可知,该方法揭示的结构失效行为可为改进变压器设计和提高设备安全性提供依据。
