Apparent critical current density(j_(Ac)^(a))of garnet all-solid-state lithium metal symmetric cells(ASSLSCs)is a fundamental parameter for designing all-solid-state lithium metal batteries.Nevertheless,how much the p...Apparent critical current density(j_(Ac)^(a))of garnet all-solid-state lithium metal symmetric cells(ASSLSCs)is a fundamental parameter for designing all-solid-state lithium metal batteries.Nevertheless,how much the possible maximum apparent current density that a given ASSLSC system can endure and how to reveal this potential still require study.Herein,a capacity perturbation strategy aiming to better measure the possible maximum j_(Ac)^(a)is proposed for the first time.With garnet-based plane-surface structure ASSLSCs as an exemplification,the j_(Ac)^(a)is quite small when the capacity is dramatically large.Under a perturbed capacity of 0.001 mA h cm^(-2),the j_(Ac)^(a)is determined to be as high as 2.35 mA cm^(-2)at room temperature.This investigation demonstrates that the capacity perturbation strategy is a feasible strategy for measuring the possible maximum j_(Ac)^(a)of Li/solid electrolyte interface,and hopefully provides good references to explore the critical current density of other types of electrochemical systems.展开更多
Childhood related diseases such as measles are characterised by short periodic outbreaks lasting about 2 weeks. This means therefore that the timescale at which such diseases operate is much shorter than the time scal...Childhood related diseases such as measles are characterised by short periodic outbreaks lasting about 2 weeks. This means therefore that the timescale at which such diseases operate is much shorter than the time scale of the human population dynamics. We analyse a compartmental model of the SIR type with periodic coefficients and different time scales for 1) disease dynamics and 2) human population dynamics. Interest is to determine the optimal vaccination strategy for such diseases. In a model with time scales, Singular Perturbation theory is used to determine stability condition for the disease free state. The stability condition is here referred to as instantaneous stability condition, and implies vaccination is done only when an instantaneous threshold condition is met. We make a comparison of disease control using the instantaneous condition to two other scenarios: one where vaccination is done constantly over time (constant vaccination strategy) and another where vaccination is done when a periodic threshold condition is satisfied (orbital stability from Floquet theory). Results show that when time scales of the disease and human population match, we see a difference in the performance of the vaccination strategies and above all, both the two threshold strategies outperform a constant vaccination strategy.展开更多
针对近地圆轨道卫星编队维持问题,开展了脉冲控制方案与维持控制策略研究,并搭建了仿真环境进行验证。根据相对轨道根数(relative orbital elements,ROEs)的状态转移方程,推导了各ROEs元素在J 2摄动下的漂移速率,并针对编队构型受到空...针对近地圆轨道卫星编队维持问题,开展了脉冲控制方案与维持控制策略研究,并搭建了仿真环境进行验证。根据相对轨道根数(relative orbital elements,ROEs)的状态转移方程,推导了各ROEs元素在J 2摄动下的漂移速率,并针对编队构型受到空间摄动的破坏问题,提出了两种不同的编队脉冲控制方案和维持策略。基于空间圆编队长期维持需求,建立了包括高精度轨道递推算法的任务仿真环境,从脉冲消耗与控制误差对提出的方案策略进行了分析讨论,验证了脉冲方案与维持策略的可行性。仿真结果表明,所提出的脉冲控制方案与维持策略具有较高的有效性及可靠性,可用于未来空间编队飞行任务。展开更多
In this paper,a sensitivity matrix based approach is proposed to improve the minimum damping ratio.The proposed method also avoids burdensome deviation calculations of damping ratio of large-scale power grids when com...In this paper,a sensitivity matrix based approach is proposed to improve the minimum damping ratio.The proposed method also avoids burdensome deviation calculations of damping ratio of large-scale power grids when compared to the Small-Signal-Stability Constrained Optimal Power Flow(SSSC-OPF)approach.This is achieved using the Matrix Perturbation Theory(MPT)to deal with the 2nd order sensitivity matrices,and the establishment of an optimal corrective control model to regulate the output power of generating units to improve the minimum damping ratio of power grids.Finally,simulation results on the IEEE 9-bus,IEEE 39-bus and a China 634-bus systems show that the proposed approach can significantly reduce the burden of deviation calculation,while enhancing power system stability and ensuring calculation accuracy.展开更多
通常的粒子群优化算法采取单一的学习策略,不利于搜索信息的有效保留,因此将改进的差分变异策略引入到粒子的速度更新中以增强算法的群体多样性;综合利用差分变异与扰动策略两种不同的产生新解的方式,提出了一种多策略交叉学习机制算法D...通常的粒子群优化算法采取单一的学习策略,不利于搜索信息的有效保留,因此将改进的差分变异策略引入到粒子的速度更新中以增强算法的群体多样性;综合利用差分变异与扰动策略两种不同的产生新解的方式,提出了一种多策略交叉学习机制算法DPPSO(hybrid particle swarm optimization with differential and perturbation)。每一个粒子通过引进的差分变异操作和扰动操作分别产生一个中间粒子,再选择较好的粒子作为当前粒子的新位置,从而实现所有粒子动态地选择更好的生成策略来更新自己的位置和速度,因此该交叉策略能够有效提高PSO算法的群体多样性和搜索路径的多样性,粒子可以获取更好的启发式信息,沿着不同的路径被引向更有潜力的搜索区域。实验结果表明了两种策略的有效性和互补性,DPPSO算法比其他三种算法有更好的综合表现,具有有效的全局收敛能力和准确定位能力。展开更多
基金the financial support from the Natural Science Foundation for Distinguished Young Scholars of Hunan Province(2020JJ2047)the science and technology innovation Program of Hunan Province(2022RC3048)+2 种基金the Program of Huxiang Young Talents(2019RS2002)the Innovation-Driven Project of Central South University(2020CX027)the Fundamental Research Funds for the Central Universities of Central South University(2021zzts0125)。
文摘Apparent critical current density(j_(Ac)^(a))of garnet all-solid-state lithium metal symmetric cells(ASSLSCs)is a fundamental parameter for designing all-solid-state lithium metal batteries.Nevertheless,how much the possible maximum apparent current density that a given ASSLSC system can endure and how to reveal this potential still require study.Herein,a capacity perturbation strategy aiming to better measure the possible maximum j_(Ac)^(a)is proposed for the first time.With garnet-based plane-surface structure ASSLSCs as an exemplification,the j_(Ac)^(a)is quite small when the capacity is dramatically large.Under a perturbed capacity of 0.001 mA h cm^(-2),the j_(Ac)^(a)is determined to be as high as 2.35 mA cm^(-2)at room temperature.This investigation demonstrates that the capacity perturbation strategy is a feasible strategy for measuring the possible maximum j_(Ac)^(a)of Li/solid electrolyte interface,and hopefully provides good references to explore the critical current density of other types of electrochemical systems.
文摘Childhood related diseases such as measles are characterised by short periodic outbreaks lasting about 2 weeks. This means therefore that the timescale at which such diseases operate is much shorter than the time scale of the human population dynamics. We analyse a compartmental model of the SIR type with periodic coefficients and different time scales for 1) disease dynamics and 2) human population dynamics. Interest is to determine the optimal vaccination strategy for such diseases. In a model with time scales, Singular Perturbation theory is used to determine stability condition for the disease free state. The stability condition is here referred to as instantaneous stability condition, and implies vaccination is done only when an instantaneous threshold condition is met. We make a comparison of disease control using the instantaneous condition to two other scenarios: one where vaccination is done constantly over time (constant vaccination strategy) and another where vaccination is done when a periodic threshold condition is satisfied (orbital stability from Floquet theory). Results show that when time scales of the disease and human population match, we see a difference in the performance of the vaccination strategies and above all, both the two threshold strategies outperform a constant vaccination strategy.
文摘针对近地圆轨道卫星编队维持问题,开展了脉冲控制方案与维持控制策略研究,并搭建了仿真环境进行验证。根据相对轨道根数(relative orbital elements,ROEs)的状态转移方程,推导了各ROEs元素在J 2摄动下的漂移速率,并针对编队构型受到空间摄动的破坏问题,提出了两种不同的编队脉冲控制方案和维持策略。基于空间圆编队长期维持需求,建立了包括高精度轨道递推算法的任务仿真环境,从脉冲消耗与控制误差对提出的方案策略进行了分析讨论,验证了脉冲方案与维持策略的可行性。仿真结果表明,所提出的脉冲控制方案与维持策略具有较高的有效性及可靠性,可用于未来空间编队飞行任务。
基金This work was supported by the National Natural Science Foundation of China(Grant No.51577085).
文摘In this paper,a sensitivity matrix based approach is proposed to improve the minimum damping ratio.The proposed method also avoids burdensome deviation calculations of damping ratio of large-scale power grids when compared to the Small-Signal-Stability Constrained Optimal Power Flow(SSSC-OPF)approach.This is achieved using the Matrix Perturbation Theory(MPT)to deal with the 2nd order sensitivity matrices,and the establishment of an optimal corrective control model to regulate the output power of generating units to improve the minimum damping ratio of power grids.Finally,simulation results on the IEEE 9-bus,IEEE 39-bus and a China 634-bus systems show that the proposed approach can significantly reduce the burden of deviation calculation,while enhancing power system stability and ensuring calculation accuracy.
文摘通常的粒子群优化算法采取单一的学习策略,不利于搜索信息的有效保留,因此将改进的差分变异策略引入到粒子的速度更新中以增强算法的群体多样性;综合利用差分变异与扰动策略两种不同的产生新解的方式,提出了一种多策略交叉学习机制算法DPPSO(hybrid particle swarm optimization with differential and perturbation)。每一个粒子通过引进的差分变异操作和扰动操作分别产生一个中间粒子,再选择较好的粒子作为当前粒子的新位置,从而实现所有粒子动态地选择更好的生成策略来更新自己的位置和速度,因此该交叉策略能够有效提高PSO算法的群体多样性和搜索路径的多样性,粒子可以获取更好的启发式信息,沿着不同的路径被引向更有潜力的搜索区域。实验结果表明了两种策略的有效性和互补性,DPPSO算法比其他三种算法有更好的综合表现,具有有效的全局收敛能力和准确定位能力。
