An anisotropic micromechanics model based on the equivalent inclusion method is developed to investigate the rafting direction of Ni-based single crystal superalloys. The micromechanical model considers actual cubic s...An anisotropic micromechanics model based on the equivalent inclusion method is developed to investigate the rafting direction of Ni-based single crystal superalloys. The micromechanical model considers actual cubic structure and orthogonal anisotropy properties. The von Mises stress, elastic strain energy density, and hydrostatic pressure in dif- ferent inclusions of micromechanical model are calculated when applying a tensile or compressive loading along the [001] direction. The calculated results can successfully pre- dict the rafting direction for alloys exhibiting a positive or a negative mismatch, which are in agreement with pervious experimental and theoretical studies. Moreover, the elastic constant differences and mismatch degree of the matrix and precipitate phases and their influences on the rafting direction are carefully discussed.展开更多
The functional regeneration of damaged axons and severed connections in the mature central nervous sys- tem (CNS) remains a challenging goal of neurological research. Mature CNS neurons are refractory to axon regene...The functional regeneration of damaged axons and severed connections in the mature central nervous sys- tem (CNS) remains a challenging goal of neurological research. Mature CNS neurons are refractory to axon regeneration for two major reasons, one, because the ac- tivity of cell-intrinsic mechanisms that drive axon growth during development is low- and often further suppressed after an injury - and two, because certain molecules that are part of mature extracellular matrix and myelin act as strong inhibitors of axon growth. Genetic removal of growth inhibitory molecules can increase axon sprouting, but is not sufficient to enable long-range axon growth. Since axon growth is robust during early developmental stages, it has long been hypothesized that mature injured neurons may be "reprogrammed" to the earlier growth state by re-activation of the intracellular growth signaling cascades that drive axon elongation in the developing fetus.展开更多
Multiproxy investigations have been performed on Core 08P23 collected from the Chukchi Plateau, the western Arctic Ocean, during the Third Chinese National Arctic Expedition. The core was dated back to Ma-rine Isotope...Multiproxy investigations have been performed on Core 08P23 collected from the Chukchi Plateau, the western Arctic Ocean, during the Third Chinese National Arctic Expedition. The core was dated back to Ma-rine Isotope Stage (MIS) 3 by a combination of Accelerator Mass Spectrometric (AMS) carbon-14 dating and regional core correlation. A total of five prominent ice-rafted detritus (IRD) events were recognized in MIS 2 and MIS 3. The IRD sources in MIS 3 are originated from vast carbonate rock outcrops of the Canadian Arctic Archipelago and clastic quartz in MIS 2 may have a Eurasian origin. Mostδ18O andδ13C values of Neogloboquadrina pachyderma (sinistral) (Nps) in Core 08P23 are lighter than the average values of surface sediments. The lighterδ18O andδ13C values of Nps in the two brown layers in MIS 1 and MIS 3 were resulted from meltwater events; and those in the gray layers in MIS 3 were caused by the enhanced sea ice formation. Theδ18O values varied inversely withδ13C in MIS 2 indicate that the study area was covered by thick sea ice or ice sheet with low temperature and little meltwater, which prevented the biological productivity and sea-atmosphere exchange, as well as water mass ventilation. The covaried light values ofδ18O andδ13C in MIS 1 and MIS 3 were resulted from meltwater and/or brine injection.展开更多
Theoretical analysis and numerical simulation have been applied to researching the effect of wave,current and wind on the ice rafting.The analytical results show that wave is the key factor for ice fracture.The proces...Theoretical analysis and numerical simulation have been applied to researching the effect of wave,current and wind on the ice rafting.The analytical results show that wave is the key factor for ice fracture.The process of ice rafting is simulated using the discrete element method.The simulated results show that the distortion or flexure breakage happens firstly,then followed by ice rafting.The comprehensively analysed results show that the ice is easily rafted on the simultaneity action of wave,current and wind,and the action of wave can't be ignored.Moreover,the rafted ice length increases with the enhancive force of ocean current and wind.展开更多
在基于三副本策略的分布式存储系统中,当存储节点上的硬盘出现故障时,常见的处理方式是等待系统预设的时间.如果该故障硬盘超时未恢复,才开始恢复故障硬盘上的副本.这种处理方式存在的问题是,当三副本组中存在故障副本时,如果该副本组...在基于三副本策略的分布式存储系统中,当存储节点上的硬盘出现故障时,常见的处理方式是等待系统预设的时间.如果该故障硬盘超时未恢复,才开始恢复故障硬盘上的副本.这种处理方式存在的问题是,当三副本组中存在故障副本时,如果该副本组再有一个副本所在的硬盘发生故障,将导致系统无法继续提供服务,且不能自动恢复.本文提出一种基于日志副本的改进的Raft共识算法,即LR-Raft (log replica based Raft),日志副本没有完整状态机,可以快速加入集群,并参与投票与共识,提升了存在故障硬盘时系统的可用性;可以解决短时间内三副本中两个副本故障导致集群不可用和丢失数据的问题.实验结果表明,在副本组中引入日志副本后,与原Raft相比,LR-Raft在不同的工作负载下读写时延均明显降低,吞吐量显著提升.展开更多
The gradual increase in shipping and drilling activities in the Arctic regions has resulted in the increased importance of studying the structural safety of polar ships in various ice conditions.Rafted ice refers to a...The gradual increase in shipping and drilling activities in the Arctic regions has resulted in the increased importance of studying the structural safety of polar ships in various ice conditions.Rafted ice refers to a type of accumulated and overlapped sea ice;it is driven by external forces,such as wind and waves,and may exert high loads on ships and threaten their structural safety.Therefore,the properties of rafted ice and the construction of numerical models should be studied before exploring the interaction and collision between ships and rafted ice.Based on the nonlinear finite-element method,this paper introduces the cohesive element model for the simulation of rafted ice.The interaction between ships and rafted ice is studied,and the ice force of the hull is obtained.Numerical simulation results are compared with model test findings,and the effectiveness of the cohesive element method in the construction of the model of rafted ice materials is verified.On this basis,a multilayer rafted ice model is constructed,and its interaction with the ship is studied.The research unveils that rafted ice parts impede crack generation and slow down crack propagation to a certain extent.展开更多
The effect of applied tensile stress on the r'-rafting behavior for a Ni-based single-crystal superalloy with more negative misfit was investigated.By conducting interrupted creep tests at high temperature,it indi...The effect of applied tensile stress on the r'-rafting behavior for a Ni-based single-crystal superalloy with more negative misfit was investigated.By conducting interrupted creep tests at high temperature,it indicated that the increase in the applied stress accelerates the r'-rafting(directional coarsening of yr phase).In the early stage of rafting,the r'-cubes start interconnecting at the ends of the parallel-to-applied-stress r'-channel.The distributions of misfit stress,coherent strain and strain energy density of the r/r'phases are then calculated by finite element analysis.The calculation results show that the rafting acceleration is mainly ascribed to the reduced strain energy density in the parallel-to-applied-stress r'-channel that is driven from the couple interaction of external load and misfit stress.Interface dislocation network formation,resulting from the misfit-induced increase in resolved shear stress,also contributes to the r'-rafting.展开更多
Organic/inorganic hybrid polymers have been widely studied for their potential use in nanocontainers and nanocarriers. In this article, one star-shaped hybrid polymer, polyhedral oligomeric silsesquioxane (POSS) gra...Organic/inorganic hybrid polymers have been widely studied for their potential use in nanocontainers and nanocarriers. In this article, one star-shaped hybrid polymer, polyhedral oligomeric silsesquioxane (POSS) grafted poly(N,N-(dimethylamino)ethyl methacrylate) (POSS-g-PDMA), was synthesized via reversible addition-fragmentation chain transfer polymerization (RAFT). The pH stimuli-responsive character of POSS-g-PDMA in aqueous solution were also studied.展开更多
基金supported by The National Natural Science Foundation of China (Grants 11102139 and 11472195)The Natural Science Foundation of Hubei Province of China (Grant 2014CFB713)
文摘An anisotropic micromechanics model based on the equivalent inclusion method is developed to investigate the rafting direction of Ni-based single crystal superalloys. The micromechanical model considers actual cubic structure and orthogonal anisotropy properties. The von Mises stress, elastic strain energy density, and hydrostatic pressure in dif- ferent inclusions of micromechanical model are calculated when applying a tensile or compressive loading along the [001] direction. The calculated results can successfully pre- dict the rafting direction for alloys exhibiting a positive or a negative mismatch, which are in agreement with pervious experimental and theoretical studies. Moreover, the elastic constant differences and mismatch degree of the matrix and precipitate phases and their influences on the rafting direction are carefully discussed.
基金funding from the National Eye Institute (R01EY022409)the Craig H. Neilsen Foundation (296098)+2 种基金the Wings for Life Foundation (WFL-US-028/14)the New York State Spinal Cord Injury Research Trust Fundthe Burke Foundation
文摘The functional regeneration of damaged axons and severed connections in the mature central nervous sys- tem (CNS) remains a challenging goal of neurological research. Mature CNS neurons are refractory to axon regeneration for two major reasons, one, because the ac- tivity of cell-intrinsic mechanisms that drive axon growth during development is low- and often further suppressed after an injury - and two, because certain molecules that are part of mature extracellular matrix and myelin act as strong inhibitors of axon growth. Genetic removal of growth inhibitory molecules can increase axon sprouting, but is not sufficient to enable long-range axon growth. Since axon growth is robust during early developmental stages, it has long been hypothesized that mature injured neurons may be "reprogrammed" to the earlier growth state by re-activation of the intracellular growth signaling cascades that drive axon elongation in the developing fetus.
基金The National Natural Science Foundation of China under contract Nos 41030859,41211120173,CHINARE2015-03-02 and IC201105the Geological Investigation Project of China Geological Survey Nos 12120113006200 and 1212011120044
文摘Multiproxy investigations have been performed on Core 08P23 collected from the Chukchi Plateau, the western Arctic Ocean, during the Third Chinese National Arctic Expedition. The core was dated back to Ma-rine Isotope Stage (MIS) 3 by a combination of Accelerator Mass Spectrometric (AMS) carbon-14 dating and regional core correlation. A total of five prominent ice-rafted detritus (IRD) events were recognized in MIS 2 and MIS 3. The IRD sources in MIS 3 are originated from vast carbonate rock outcrops of the Canadian Arctic Archipelago and clastic quartz in MIS 2 may have a Eurasian origin. Mostδ18O andδ13C values of Neogloboquadrina pachyderma (sinistral) (Nps) in Core 08P23 are lighter than the average values of surface sediments. The lighterδ18O andδ13C values of Nps in the two brown layers in MIS 1 and MIS 3 were resulted from meltwater events; and those in the gray layers in MIS 3 were caused by the enhanced sea ice formation. Theδ18O values varied inversely withδ13C in MIS 2 indicate that the study area was covered by thick sea ice or ice sheet with low temperature and little meltwater, which prevented the biological productivity and sea-atmosphere exchange, as well as water mass ventilation. The covaried light values ofδ18O andδ13C in MIS 1 and MIS 3 were resulted from meltwater and/or brine injection.
基金The National Natural Science Foundation of China under contract Nos 40506009 and 908-02-03’ National Project
文摘Theoretical analysis and numerical simulation have been applied to researching the effect of wave,current and wind on the ice rafting.The analytical results show that wave is the key factor for ice fracture.The process of ice rafting is simulated using the discrete element method.The simulated results show that the distortion or flexure breakage happens firstly,then followed by ice rafting.The comprehensively analysed results show that the ice is easily rafted on the simultaneity action of wave,current and wind,and the action of wave can't be ignored.Moreover,the rafted ice length increases with the enhancive force of ocean current and wind.
文摘在基于三副本策略的分布式存储系统中,当存储节点上的硬盘出现故障时,常见的处理方式是等待系统预设的时间.如果该故障硬盘超时未恢复,才开始恢复故障硬盘上的副本.这种处理方式存在的问题是,当三副本组中存在故障副本时,如果该副本组再有一个副本所在的硬盘发生故障,将导致系统无法继续提供服务,且不能自动恢复.本文提出一种基于日志副本的改进的Raft共识算法,即LR-Raft (log replica based Raft),日志副本没有完整状态机,可以快速加入集群,并参与投票与共识,提升了存在故障硬盘时系统的可用性;可以解决短时间内三副本中两个副本故障导致集群不可用和丢失数据的问题.实验结果表明,在副本组中引入日志副本后,与原Raft相比,LR-Raft在不同的工作负载下读写时延均明显降低,吞吐量显著提升.
基金The National Natural Science Foundation of China(Grant Nos.52192693,52192690,51979051,51979056 and U20A20327)the National Key Research and Development Program of China(Grant No.2021YFC2803400)。
文摘The gradual increase in shipping and drilling activities in the Arctic regions has resulted in the increased importance of studying the structural safety of polar ships in various ice conditions.Rafted ice refers to a type of accumulated and overlapped sea ice;it is driven by external forces,such as wind and waves,and may exert high loads on ships and threaten their structural safety.Therefore,the properties of rafted ice and the construction of numerical models should be studied before exploring the interaction and collision between ships and rafted ice.Based on the nonlinear finite-element method,this paper introduces the cohesive element model for the simulation of rafted ice.The interaction between ships and rafted ice is studied,and the ice force of the hull is obtained.Numerical simulation results are compared with model test findings,and the effectiveness of the cohesive element method in the construction of the model of rafted ice materials is verified.On this basis,a multilayer rafted ice model is constructed,and its interaction with the ship is studied.The research unveils that rafted ice parts impede crack generation and slow down crack propagation to a certain extent.
基金National Natural Science Foundation of China(Nos.U1435207,51771007,51671015)National Defense Basic Scientific Research Project(No.A2120132006).
文摘The effect of applied tensile stress on the r'-rafting behavior for a Ni-based single-crystal superalloy with more negative misfit was investigated.By conducting interrupted creep tests at high temperature,it indicated that the increase in the applied stress accelerates the r'-rafting(directional coarsening of yr phase).In the early stage of rafting,the r'-cubes start interconnecting at the ends of the parallel-to-applied-stress r'-channel.The distributions of misfit stress,coherent strain and strain energy density of the r/r'phases are then calculated by finite element analysis.The calculation results show that the rafting acceleration is mainly ascribed to the reduced strain energy density in the parallel-to-applied-stress r'-channel that is driven from the couple interaction of external load and misfit stress.Interface dislocation network formation,resulting from the misfit-induced increase in resolved shear stress,also contributes to the r'-rafting.
基金supported by the Guangdong Province Research Project(No.2011A091000007)the National Natural Science Foundation of China for its financial support(No.21174162)
文摘Organic/inorganic hybrid polymers have been widely studied for their potential use in nanocontainers and nanocarriers. In this article, one star-shaped hybrid polymer, polyhedral oligomeric silsesquioxane (POSS) grafted poly(N,N-(dimethylamino)ethyl methacrylate) (POSS-g-PDMA), was synthesized via reversible addition-fragmentation chain transfer polymerization (RAFT). The pH stimuli-responsive character of POSS-g-PDMA in aqueous solution were also studied.