Dirac semimetals are materials in which the conduction and the valence bands have robust crossing points protected by topology or symmetry. Recently, a new type of Dirac semimetals, so called the Dirac line-node semim...Dirac semimetals are materials in which the conduction and the valence bands have robust crossing points protected by topology or symmetry. Recently, a new type of Dirac semimetals, so called the Dirac line-node semimetals （DLNSs）, have attracted a lot of attention, as they host robust Dirac points along the one-dimensional （1D） lines in the Brillouin zone （BZ）. In this work, using angle-resolved photoemission spectroscopy （ARPES） and first-principles calculations, we systematically investigated the electronic structures of non-symmorphic ZrSiS crystal where we clearly distinguished the surface states from the bulk states. The photon-energy-dependent measurements further prove the existence of Dirac line node along the X-R direction. Remarkably, by in situ surface potassium doping, we clearly observed the different evolutions of the bulk and surface electronic states while proving the robustness of the Dirac line node. Our studies not only reveal the complete electronic structures of ZrSiS, but also demonstrate the method manipulating the electronic structure of the compound.展开更多
配电网中关键节点与主干线路的失效可能引发电网大规模故障,对供电可靠性构成严重威胁。为有效识别配电网薄弱环节,提出一套适用于网架数字化建模与脆弱性评估的节点与线路脆弱性指标体系。对于节点脆弱性评估,除对传统指标(如节点度数...配电网中关键节点与主干线路的失效可能引发电网大规模故障,对供电可靠性构成严重威胁。为有效识别配电网薄弱环节,提出一套适用于网架数字化建模与脆弱性评估的节点与线路脆弱性指标体系。对于节点脆弱性评估,除对传统指标(如节点度数、节点介数、节点紧密中心度、节点注入功率及电压偏离度)进行优化外,进一步引入基于空间直接估计(spatial direct estimation,SDE)的结构脆弱性指标,以及考虑线路越限风险的抗扰动脆弱性指标;对于线路脆弱性评估,构建了线路度数、线路介数和线路SDE三类指标。基于上述指标体系,采用熵权法与直接赋权法分别确定节点与线路脆弱度权重,进而计算节点与线路的综合脆弱性评分。最后,以IEEE33节点系统和某中型城市中心城区实际配电网为例进行仿真验证,结果表明所提方法能有效辨识配电网节点与线路的薄弱环节,及时发现潜在运行隐患。展开更多
针对无线和电力线通信混合组网的信道竞争接入问题,提出了一种基于深度强化学习的电力线与无线双模通信的MAC接入算法。双模节点根据网络广播信息和信道使用等数据自适应接入双媒质信道。首先建立了基于双模通信网络交互和统计信息的双...针对无线和电力线通信混合组网的信道竞争接入问题,提出了一种基于深度强化学习的电力线与无线双模通信的MAC接入算法。双模节点根据网络广播信息和信道使用等数据自适应接入双媒质信道。首先建立了基于双模通信网络交互和统计信息的双模通信节点数据采集模型;接着定义了基于协作信息的深度强化学习(deep reinforcement learning,DRL)状态空间、动作空间和奖励,设计了联合α-公平效用函数和P坚持接入机制的节点决策流程,实现基于双深度Q网络(double deep Q-network,DDQN)的双模节点自适应接入算法;最后进行算法性能仿真和对比分析。仿真结果表明,提出的接入算法能够在保证双模网络和信道接入公平性的条件下,有效提高双模通信节点的接入性能。展开更多
基金Project supported by the National Key R&D Program of China(Grant No.2017YFA0305400)Chinese Academy of Science–Shanghai Science Research Center(Grant No.CAS-SSRC-YH-2015-01)+2 种基金the National Natural Science Foundation of China(Grant No.11674229)the Engineering and Physical Sciences Research Council Platform(Grant No.EP/M020517/1)the Hefei Science–Center Chinese Academy of Sciences(Grant No.2015HSC-UE013)
文摘Dirac semimetals are materials in which the conduction and the valence bands have robust crossing points protected by topology or symmetry. Recently, a new type of Dirac semimetals, so called the Dirac line-node semimetals （DLNSs）, have attracted a lot of attention, as they host robust Dirac points along the one-dimensional （1D） lines in the Brillouin zone （BZ）. In this work, using angle-resolved photoemission spectroscopy （ARPES） and first-principles calculations, we systematically investigated the electronic structures of non-symmorphic ZrSiS crystal where we clearly distinguished the surface states from the bulk states. The photon-energy-dependent measurements further prove the existence of Dirac line node along the X-R direction. Remarkably, by in situ surface potassium doping, we clearly observed the different evolutions of the bulk and surface electronic states while proving the robustness of the Dirac line node. Our studies not only reveal the complete electronic structures of ZrSiS, but also demonstrate the method manipulating the electronic structure of the compound.
文摘配电网中关键节点与主干线路的失效可能引发电网大规模故障,对供电可靠性构成严重威胁。为有效识别配电网薄弱环节,提出一套适用于网架数字化建模与脆弱性评估的节点与线路脆弱性指标体系。对于节点脆弱性评估,除对传统指标(如节点度数、节点介数、节点紧密中心度、节点注入功率及电压偏离度)进行优化外,进一步引入基于空间直接估计(spatial direct estimation,SDE)的结构脆弱性指标,以及考虑线路越限风险的抗扰动脆弱性指标;对于线路脆弱性评估,构建了线路度数、线路介数和线路SDE三类指标。基于上述指标体系,采用熵权法与直接赋权法分别确定节点与线路脆弱度权重,进而计算节点与线路的综合脆弱性评分。最后,以IEEE33节点系统和某中型城市中心城区实际配电网为例进行仿真验证,结果表明所提方法能有效辨识配电网节点与线路的薄弱环节,及时发现潜在运行隐患。
文摘针对无线和电力线通信混合组网的信道竞争接入问题,提出了一种基于深度强化学习的电力线与无线双模通信的MAC接入算法。双模节点根据网络广播信息和信道使用等数据自适应接入双媒质信道。首先建立了基于双模通信网络交互和统计信息的双模通信节点数据采集模型;接着定义了基于协作信息的深度强化学习(deep reinforcement learning,DRL)状态空间、动作空间和奖励,设计了联合α-公平效用函数和P坚持接入机制的节点决策流程,实现基于双深度Q网络(double deep Q-network,DDQN)的双模节点自适应接入算法;最后进行算法性能仿真和对比分析。仿真结果表明,提出的接入算法能够在保证双模网络和信道接入公平性的条件下,有效提高双模通信节点的接入性能。
