The scaling relations among the mean end-to-end distance of polymer along the channel<R||>,the polymer length N,and the effective diameter of channel De were investigated for flexible and semi-flexible polymer c...The scaling relations among the mean end-to-end distance of polymer along the channel<R||>,the polymer length N,and the effective diameter of channel De were investigated for flexible and semi-flexible polymer chains confined in long cylindrical channels.For the flexible polymer chain,scaling relation<R||>~NDe–0.7 was found in the classic de Gennes regime at lp2/b<De<Rg with lp the persistence length,b the bond length,and Rg the radius of gyration of polymer.For the semi-flexible polymer,<R||>~NDe–1 in the transition regime lp<De<xlp(x>1)and<R|>~De–0.7 in the classic de Gennes regime at larger De>xlp were observed.The simulation results revealed that the scaling relation in the transition regime was due to the rod-like behavior of the semi-flexible polymer in the small regime lp<De<xlp.展开更多
Considering the self-fields of relativistic electron beam （REB）, the electron beam injected in plasma will form an ion-channel, which can stably guide REB transmitted in plasma. Based on the effect of ion-channel, t...Considering the self-fields of relativistic electron beam （REB）, the electron beam injected in plasma will form an ion-channel, which can stably guide REB transmitted in plasma. Based on the effect of ion-channel, the EM dispersion characteristics in a dielectric waveguide filled with plasmas is studied by using linear electromagnetic （EM） hydrodynamics perturbation theory. Both the TM mode dispersion equation and the dispersion relation are derived. After that, a discussion on the conditions of Cherenkov radiation in this system is given. It was found that the betatron oscillation of the REB is one of the important factors for the slow-wave EM instability in this system. The dispersion relation is of the form of electromagnetic-electrostatic （EM-ES） hybrid mode, which is different from the case where the effect of the ion channel is neglected.展开更多
A new Reynolds stress constitutive formula is constructed using the first- order statistics of turbulent fluctuations instead of the mean strain rate. It includes zero empirical coefficients. The formula is validated ...A new Reynolds stress constitutive formula is constructed using the first- order statistics of turbulent fluctuations instead of the mean strain rate. It includes zero empirical coefficients. The formula is validated with the direct numerical simulation （DNS） data of turbulent channel flow at Reτ=180. The Reynolds stresses given by the proposed formula agree very well with the DNS results. The good agreement persists even after the multi-angle rotation of the coordinate system, indicating the rotation in- variance of the formula. The autocorrelation of the fluctuating velocity rather than the mean strain rate is close to the essence of the Reynolds stress.展开更多
A new turbulent constitutive relation was directly derived from Boussinesqs hypothesis and mixing length theory,and then implemented in the standard k-ε model.The performance of this constitutive relation was valid...A new turbulent constitutive relation was directly derived from Boussinesqs hypothesis and mixing length theory,and then implemented in the standard k-ε model.The performance of this constitutive relation was validated in zero pressure gradient flat-plate boundary layer flow,fully-developed turbulent channel flow and separated flow in a plane asymmetric diffuser.The investigation demonstrated that,this new constitutive relation gave very accurate results in the former two basic cases and provided significant improvement in prediction of separated and reattachment points in the plane asymmetric diffuser.Separation and reattachment points at x/H =7.5and 29 were calculated accurately in comparison to experimental results,and the static pressure coefficient of 0.82 was very close to large eddy simulation calculation.These results are very encouraging but further verification and extensive application of the new constitutive relation to other two-equation eddy viscosity model are needed.展开更多
生物医学研究人员经常搜索大量文献,寻找生物实体之间的作用关系,如:药物-药物、化合物-蛋白质等作用关系。随着医学文献的激增和深度学习的发展,自动从文献中提取生物实体作用关系已经显示出巨大潜力。以往使用深度学习的方法取得了一...生物医学研究人员经常搜索大量文献,寻找生物实体之间的作用关系,如:药物-药物、化合物-蛋白质等作用关系。随着医学文献的激增和深度学习的发展,自动从文献中提取生物实体作用关系已经显示出巨大潜力。以往使用深度学习的方法取得了一定效果,但存在以下问题:模型采用静态词向量,不能区分一词多义;未考虑单词的权重,对长句子提取效果较差;通过多种模型集成来改善样本不平衡问题,模型较为复杂。为此提出一种基于残差结构的深层多通道CNN模型(MCCNN),通过BERT(Bidirectional Encoder Representation from Transformers)产生动态词向量来提高词汇语义表示的准确性,利用多头注意力捕获长句子的依赖并通过设计Ranking损失函数代替多模型集成来降低样本不平衡的影响。在多个数据集上进行测试,结果表明提出的方法具有较好的效果。展开更多
基金financially supported by the National Natural Science Foundation of China (Nos. 21574117 and 11674277)Zhejiang Provincial Natural Science Foundation of China (No. LY16A040004)
文摘The scaling relations among the mean end-to-end distance of polymer along the channel<R||>,the polymer length N,and the effective diameter of channel De were investigated for flexible and semi-flexible polymer chains confined in long cylindrical channels.For the flexible polymer chain,scaling relation<R||>~NDe–0.7 was found in the classic de Gennes regime at lp2/b<De<Rg with lp the persistence length,b the bond length,and Rg the radius of gyration of polymer.For the semi-flexible polymer,<R||>~NDe–1 in the transition regime lp<De<xlp(x>1)and<R|>~De–0.7 in the classic de Gennes regime at larger De>xlp were observed.The simulation results revealed that the scaling relation in the transition regime was due to the rod-like behavior of the semi-flexible polymer in the small regime lp<De<xlp.
基金supported by National Natural Science Foundation of China(Nos.11075123 and 51207171)
文摘Considering the self-fields of relativistic electron beam （REB）, the electron beam injected in plasma will form an ion-channel, which can stably guide REB transmitted in plasma. Based on the effect of ion-channel, the EM dispersion characteristics in a dielectric waveguide filled with plasmas is studied by using linear electromagnetic （EM） hydrodynamics perturbation theory. Both the TM mode dispersion equation and the dispersion relation are derived. After that, a discussion on the conditions of Cherenkov radiation in this system is given. It was found that the betatron oscillation of the REB is one of the important factors for the slow-wave EM instability in this system. The dispersion relation is of the form of electromagnetic-electrostatic （EM-ES） hybrid mode, which is different from the case where the effect of the ion channel is neglected.
基金Project supported by the National Natural Science Foundation of China(No.11002014)
文摘A new Reynolds stress constitutive formula is constructed using the first- order statistics of turbulent fluctuations instead of the mean strain rate. It includes zero empirical coefficients. The formula is validated with the direct numerical simulation （DNS） data of turbulent channel flow at Reτ=180. The Reynolds stresses given by the proposed formula agree very well with the DNS results. The good agreement persists even after the multi-angle rotation of the coordinate system, indicating the rotation in- variance of the formula. The autocorrelation of the fluctuating velocity rather than the mean strain rate is close to the essence of the Reynolds stress.
基金China Academy of Aeronautics Propulsion Innovation Fund
文摘A new turbulent constitutive relation was directly derived from Boussinesqs hypothesis and mixing length theory,and then implemented in the standard k-ε model.The performance of this constitutive relation was validated in zero pressure gradient flat-plate boundary layer flow,fully-developed turbulent channel flow and separated flow in a plane asymmetric diffuser.The investigation demonstrated that,this new constitutive relation gave very accurate results in the former two basic cases and provided significant improvement in prediction of separated and reattachment points in the plane asymmetric diffuser.Separation and reattachment points at x/H =7.5and 29 were calculated accurately in comparison to experimental results,and the static pressure coefficient of 0.82 was very close to large eddy simulation calculation.These results are very encouraging but further verification and extensive application of the new constitutive relation to other two-equation eddy viscosity model are needed.
文摘生物医学研究人员经常搜索大量文献,寻找生物实体之间的作用关系,如:药物-药物、化合物-蛋白质等作用关系。随着医学文献的激增和深度学习的发展,自动从文献中提取生物实体作用关系已经显示出巨大潜力。以往使用深度学习的方法取得了一定效果,但存在以下问题:模型采用静态词向量,不能区分一词多义;未考虑单词的权重,对长句子提取效果较差;通过多种模型集成来改善样本不平衡问题,模型较为复杂。为此提出一种基于残差结构的深层多通道CNN模型(MCCNN),通过BERT(Bidirectional Encoder Representation from Transformers)产生动态词向量来提高词汇语义表示的准确性,利用多头注意力捕获长句子的依赖并通过设计Ranking损失函数代替多模型集成来降低样本不平衡的影响。在多个数据集上进行测试,结果表明提出的方法具有较好的效果。
