The perturbation method is used to study the localization of electric field distribution and the effective nonlinear response of graded composites under an external alternating-current（AC） and direct-current（DC） e...The perturbation method is used to study the localization of electric field distribution and the effective nonlinear response of graded composites under an external alternating-current（AC） and direct-current（DC） electric field E app = E 0（1 ＋ sin ωt）.The dielectric profile of the cylindrical inclusions is modeled by function ε i（r） = C k r k（r ≤ a）,where r is the radius of the cylindrical inclusion,and C k,k,a are parameters.In the dilute limit,the local potentials and the effective nonlinear responses at all harmonics are derived.Meanwhile,the general effective nonlinear responses are also derived and compared with the effective nonlinear responses at harmonics under the AC and DC external field.It is found that the effective nonlinear AC and DC responses at harmonics can be calculated by those of the general effective nonlinear of the graded composites under the external DC electric field.Moreover,the obtained local electrical fields show that the electrical field distribution in the cylindrical inclusions is controllable,and the maximum of the electric field inside the cylinder is at its center.展开更多
The attosecond ionization dynamics of atoms has attracted extensive attention in these days.However,the role of the initial state is not clearly understood.To address this question,we perform simulations on the neon a...The attosecond ionization dynamics of atoms has attracted extensive attention in these days.However,the role of the initial state is not clearly understood.To address this question,we perform simulations on the neon atom and its model atom with different initial states by numerically solving the corresponding two-dimensional time-dependent Schrodinger¨equations.We theoretically investigate atomic photoelectron momentum distributions(PMDs)by a pair of elliptically polarized attosecond laser pulses.We find that the PMD is sensitive not only to the ellipticities of the pulses,the relative helicity,and time delay of the pulses,but also to the symmetry of the initial electronic states.Results are analyzed by the first-order time-dependent perturbation theory(TDPT)and offer a new tool for detecting the rotation direction of the ring currents.展开更多
现有的监控方法存在较大的误差,因此对物联网技术下的变电站通信分布式直流电源远程监控进行研究。通过应用物联网技术与射频识别(Radio Frequency Identification,RFID)标签,数据采集速率大幅提高,传感器节点协同感知网络状态,并以多...现有的监控方法存在较大的误差,因此对物联网技术下的变电站通信分布式直流电源远程监控进行研究。通过应用物联网技术与射频识别(Radio Frequency Identification,RFID)标签,数据采集速率大幅提高,传感器节点协同感知网络状态,并以多种报表形式呈现数据,清晰展示直流屏历史运行数据。在稳压电源中,采用直流分组放电法计算内阻值,监控单体电池的电压均衡性,并与设定的阈值比较,准确判断直流电源系统的实时运行状况,实现全面监控。测试结果表明,电池组的内阻值误差小于0.1%,放电容量与设定一致,确保电源电压和容量均衡,实现变电站的安全稳定运行。展开更多
分布式一致性控制因其灵活性和协同能力成为多端柔性直流(multi-terminal flexible direct current,MTDC)系统二次频率控制的新选择。然而,分布式控制结构虽提高了MTDC系统调频能力,但也带来了网络攻击的威胁。为此,该文首先研究了常值...分布式一致性控制因其灵活性和协同能力成为多端柔性直流(multi-terminal flexible direct current,MTDC)系统二次频率控制的新选择。然而,分布式控制结构虽提高了MTDC系统调频能力,但也带来了网络攻击的威胁。为此,该文首先研究了常值虚假信息注入(false data injection,FDI)攻击对分布式二次控制器的不利影响,分析表明受FDI攻击的站点会持续存在与攻击向量有关的频率偏差。进而为消除攻击造成的频率偏差,该文利用常值微分为0的特性提出了一种抵御常值FDI攻击的分布式一致性控制策略,并从理论上证明了所提策略能消除FDI攻击引起的偏差。最后基于MATLAB/SIMULINK搭建了四端柔性直流系统仿真模型,分别进行单换流站遭受攻击、全部换流站同时遭受攻击及全部换流站在不同时间遭受攻击的3种攻击场景仿真。仿真结果表明所提控制策略在3种场景下均能消除FDI攻击影响,使MTDC系统实现二次调频。展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.40876094 and JQ10974106)the National High Technology Research and Development Program of China(Grant Nos.2009AA09Z102 and 2008AA09A403)+1 种基金the Excellent Youth Fundation of Shandong Scientific Committee,China(Grant No.JQ201018)the Natural Science Foundation of Shandong Province,China(Grant No.ZR2009AZ002)
文摘The perturbation method is used to study the localization of electric field distribution and the effective nonlinear response of graded composites under an external alternating-current（AC） and direct-current（DC） electric field E app = E 0（1 ＋ sin ωt）.The dielectric profile of the cylindrical inclusions is modeled by function ε i（r） = C k r k（r ≤ a）,where r is the radius of the cylindrical inclusion,and C k,k,a are parameters.In the dilute limit,the local potentials and the effective nonlinear responses at all harmonics are derived.Meanwhile,the general effective nonlinear responses are also derived and compared with the effective nonlinear responses at harmonics under the AC and DC external field.It is found that the effective nonlinear AC and DC responses at harmonics can be calculated by those of the general effective nonlinear of the graded composites under the external DC electric field.Moreover,the obtained local electrical fields show that the electrical field distribution in the cylindrical inclusions is controllable,and the maximum of the electric field inside the cylinder is at its center.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11404204 and 11974229)the Natural Science Foundation for Young Scientists of Shanxi Province,China(Grant No.201901D211404)+1 种基金the Scientific and Technological Innovation Program of Higher Education Institutions in Shanxi Province,China(Grant No.2019L0468)the Project of Excellent Course of Shanxi Normal University,China(Grant No.2017YZKC-35).
文摘The attosecond ionization dynamics of atoms has attracted extensive attention in these days.However,the role of the initial state is not clearly understood.To address this question,we perform simulations on the neon atom and its model atom with different initial states by numerically solving the corresponding two-dimensional time-dependent Schrodinger¨equations.We theoretically investigate atomic photoelectron momentum distributions(PMDs)by a pair of elliptically polarized attosecond laser pulses.We find that the PMD is sensitive not only to the ellipticities of the pulses,the relative helicity,and time delay of the pulses,but also to the symmetry of the initial electronic states.Results are analyzed by the first-order time-dependent perturbation theory(TDPT)and offer a new tool for detecting the rotation direction of the ring currents.
文摘现有的监控方法存在较大的误差,因此对物联网技术下的变电站通信分布式直流电源远程监控进行研究。通过应用物联网技术与射频识别(Radio Frequency Identification,RFID)标签,数据采集速率大幅提高,传感器节点协同感知网络状态,并以多种报表形式呈现数据,清晰展示直流屏历史运行数据。在稳压电源中,采用直流分组放电法计算内阻值,监控单体电池的电压均衡性,并与设定的阈值比较,准确判断直流电源系统的实时运行状况,实现全面监控。测试结果表明,电池组的内阻值误差小于0.1%,放电容量与设定一致,确保电源电压和容量均衡,实现变电站的安全稳定运行。
文摘分布式一致性控制因其灵活性和协同能力成为多端柔性直流(multi-terminal flexible direct current,MTDC)系统二次频率控制的新选择。然而,分布式控制结构虽提高了MTDC系统调频能力,但也带来了网络攻击的威胁。为此,该文首先研究了常值虚假信息注入(false data injection,FDI)攻击对分布式二次控制器的不利影响,分析表明受FDI攻击的站点会持续存在与攻击向量有关的频率偏差。进而为消除攻击造成的频率偏差,该文利用常值微分为0的特性提出了一种抵御常值FDI攻击的分布式一致性控制策略,并从理论上证明了所提策略能消除FDI攻击引起的偏差。最后基于MATLAB/SIMULINK搭建了四端柔性直流系统仿真模型,分别进行单换流站遭受攻击、全部换流站同时遭受攻击及全部换流站在不同时间遭受攻击的3种攻击场景仿真。仿真结果表明所提控制策略在3种场景下均能消除FDI攻击影响,使MTDC系统实现二次调频。
