Recently, the concept of topological insulators has been generalized to topological semimetals, including three-dimensional （3D） Weyl semimetals, 3D Dirac semimetMs, and 3D node-line semimetals （NLSs）. In particul...Recently, the concept of topological insulators has been generalized to topological semimetals, including three-dimensional （3D） Weyl semimetals, 3D Dirac semimetMs, and 3D node-line semimetals （NLSs）. In particular, several compounds （e.g., certain 3D graphene networks, Cu3PdN, Ca3P2 ） were discovered to be 3D NLSs, in which the conduction and valence bands cross at closed lines in the Brillouin zone. Except for the two-dimensional （2D） Dirac semimetal （e.g., graphene）, 2D topological semimetals are much less investigated. Here we propose a new concept of a 2D NLS and suggest that this state could be realized in a new mixed lattice （named as HK lattice） composed by Kagome and honeycomb lattices. It is found that A3B2 （A is a group-liB cation and B is a group-VA anion） compounds （such as Hg3As2） with the HK lattice are 2D NLSs due to the band inversion between the cation Hg-s orbital and the anion As-pz orbital with respect to the mirror symmetry. Since the band inversion occurs between two bands with the same parity, this peculiar 2D NLS could be used as transparent conductors. In the presence of buckling or spin-orbit coupling, the 2D NLS state may turn into a 2D Dirac semimetal state or a 2D topological crystalline insulating state. Since the band gap opening due to buckling or spin-orbit coupling is small, Hg3As3 with the HK lattice can still be regarded as a 2D NLS at room temperature. Our work suggests a new route to design topological materials without involving states with opposite parities.展开更多
为了加快大型风电场的仿真速率,提出了一种基于等效短线路解耦的模型分割方案。首先对于机组类型单一的大型风电场,采用输出倍乘与集电线路等值的方法进行简化建模。在此基础上,针对风电场内线路较短,难以采用长输电线路自然解耦来并行...为了加快大型风电场的仿真速率,提出了一种基于等效短线路解耦的模型分割方案。首先对于机组类型单一的大型风电场,采用输出倍乘与集电线路等值的方法进行简化建模。在此基础上,针对风电场内线路较短,难以采用长输电线路自然解耦来并行运算的缺点,提出对等值后的机组连接线与连接升压站的长汇集线之间进行参数补偿,从而满足输电线路在一个步长上的解耦判据。在Matlab/Simulink搭建仿真模型,对模型分割前后进行了对比。仿真结果验证了所提方案的可行性。在此基础上采用状态空间节点(state space node,SSN)法对风电机组内部划分群组,最终在RT-LAB平台上实现了大型海上风电场的实时化仿真。展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 11374056the Special Funds for Major State Basic Research under Grant No 2015CB921700+1 种基金the Program for Professor of Special Appointment(Eastern Scholar)the Qing Nian Ba Jian Program,and the Fok Ying Tung Education Foundation
文摘Recently, the concept of topological insulators has been generalized to topological semimetals, including three-dimensional （3D） Weyl semimetals, 3D Dirac semimetMs, and 3D node-line semimetals （NLSs）. In particular, several compounds （e.g., certain 3D graphene networks, Cu3PdN, Ca3P2 ） were discovered to be 3D NLSs, in which the conduction and valence bands cross at closed lines in the Brillouin zone. Except for the two-dimensional （2D） Dirac semimetal （e.g., graphene）, 2D topological semimetals are much less investigated. Here we propose a new concept of a 2D NLS and suggest that this state could be realized in a new mixed lattice （named as HK lattice） composed by Kagome and honeycomb lattices. It is found that A3B2 （A is a group-liB cation and B is a group-VA anion） compounds （such as Hg3As2） with the HK lattice are 2D NLSs due to the band inversion between the cation Hg-s orbital and the anion As-pz orbital with respect to the mirror symmetry. Since the band inversion occurs between two bands with the same parity, this peculiar 2D NLS could be used as transparent conductors. In the presence of buckling or spin-orbit coupling, the 2D NLS state may turn into a 2D Dirac semimetal state or a 2D topological crystalline insulating state. Since the band gap opening due to buckling or spin-orbit coupling is small, Hg3As3 with the HK lattice can still be regarded as a 2D NLS at room temperature. Our work suggests a new route to design topological materials without involving states with opposite parities.
文摘为了加快大型风电场的仿真速率,提出了一种基于等效短线路解耦的模型分割方案。首先对于机组类型单一的大型风电场,采用输出倍乘与集电线路等值的方法进行简化建模。在此基础上,针对风电场内线路较短,难以采用长输电线路自然解耦来并行运算的缺点,提出对等值后的机组连接线与连接升压站的长汇集线之间进行参数补偿,从而满足输电线路在一个步长上的解耦判据。在Matlab/Simulink搭建仿真模型,对模型分割前后进行了对比。仿真结果验证了所提方案的可行性。在此基础上采用状态空间节点(state space node,SSN)法对风电机组内部划分群组,最终在RT-LAB平台上实现了大型海上风电场的实时化仿真。
