The base of the ICS(International Commission on Stratigraphy)Geological Time Scale was ratified in 2022 by defining a new Global Stratigraphic Standard Age(GSSA)for the lower boundary of the Hadean Eon(formerly 4000–...The base of the ICS(International Commission on Stratigraphy)Geological Time Scale was ratified in 2022 by defining a new Global Stratigraphic Standard Age(GSSA)for the lower boundary of the Hadean Eon(formerly 4000–3600 Ma);the age of the Solar System based on the oldest solids,calcium-aluminium inclusions(CAIs),generated in the protoplanetary disk.The formal GSSA for the Hadean base is the oldest reliable,weighted mean Ucorrected Pb–Pb age of 4567.30±0.16 Ma obtained for CAIs in primitive meteorites Allende and Efremovka.This age is supported by the 4568–4567 Ma U-corrected Pb–Pb ages of chondrules in Northwest African meteorites.The boundary sets an upper lifetime for the protoplanetary disk and timing of planet formation.展开更多
The Anthropocene as a prospective new,ongoing series/epoch must be defensible against all relevant concerns.We address the seven,still-relevant challenges posed to the Anthropocene Working Group by the Chair,Internati...The Anthropocene as a prospective new,ongoing series/epoch must be defensible against all relevant concerns.We address the seven,still-relevant challenges posed to the Anthropocene Working Group by the Chair,International Commission on Stratigraphy(ICS),in 2014.(1)Concept or reality?The Anthropocene possesses a substantial,sharply distinctive stratigraphic record recognisable through many proxy signals from the mid-20th century onwards;(2)GSSP or GSSA?The Anthropocene can be defined by a GSSP and correlated globally;(3)Past or future?The Anthropocene unquestionably represents geological time,its transformations having already moved the Earth System beyond Holocene norms towards an irreversible future trajectory;(4)Utility?The Anthropocene’s distinctive material content allows useful delineation on geological sections/maps;(5)Indelibility?Many of the Anthropocene’s transformative effects cannot be subsequently effaced or overprinted;(6)Fit within the Geological Time Scale(GTS)?The Anthropocene represents a unique,youngest,interval in Earth history and strata of profound significance;(7)What is its value?The chronostratigraphic Anthropocene has conceptual usefulness even informally,but would then lack the clarity,stability and recognition that formalization provides.Without its formalization,the GTS would no longer accurately reflect Earth history,diminishing the relevance of geological science for analysis of ongoing planetary change.展开更多
CLC谐振型感应电能传输系统较传统的LC谐振型系统具有更大的谐振容量和更小的频率漂移,但由于系统的高阶及多周期点特性,对CLC型系统的控制更为困难。为实现CLC谐振型系统的输出鲁棒控制,将系统状态变量及非线性开关函数进行频域线性化...CLC谐振型感应电能传输系统较传统的LC谐振型系统具有更大的谐振容量和更小的频率漂移,但由于系统的高阶及多周期点特性,对CLC型系统的控制更为困难。为实现CLC谐振型系统的输出鲁棒控制,将系统状态变量及非线性开关函数进行频域线性化,通过平衡点变换,得到平衡点附近的广义状态空间平均(generalized state space averaging,GSSA)扰动模型。建立了系统的H∞控制系统结构,提出GSSA模型误差扰动有界定理并给出了证明。给出了相应的H∞扰动控制律,并通过仿真及实验结果验证了该模型及控制方法的有效性。展开更多
在型谐振感应电能传输(inductive power transfer,IPT)系统中,由于负载及耦合参数变化,导致系统谐振频率产生随机漂移。针对频率不确定条件下的输出控制,利用广义状态空间平均(generalized state space averaging,GSSA)法对系统进行频...在型谐振感应电能传输(inductive power transfer,IPT)系统中,由于负载及耦合参数变化,导致系统谐振频率产生随机漂移。针对频率不确定条件下的输出控制,利用广义状态空间平均(generalized state space averaging,GSSA)法对系统进行频域建模,将状态变量进行频域展开获得广义状态变量,从而获得线性状态空间模型。借助线性分式变换,将GSSA模型的确定部分与不确定部分分离,从而将系统的不确定模型转化为含摄动反馈的线性动力学系统。在此基础上提出一种基于GSSA模型的H_∞控制方法,又基于频域设计出混合灵敏度H_∞控制器,实现了多变量无静差跟踪鲁棒控制,并利用结构奇异值分析方法校验了鲁棒控制器的稳定性及性能。仿真及实验结果验证了其可行性。展开更多
感应电能传输(inductive power transfer,IPT)技术应用于移动负载供电时,由于其能量传输的方向性限制,不可避免的振动、偏转等机械扰动容易导致系统传输功率的不稳定。主要针对移动负载供电时外部扰动带来的互感扰动问题,设计了一种适...感应电能传输(inductive power transfer,IPT)技术应用于移动负载供电时,由于其能量传输的方向性限制,不可避免的振动、偏转等机械扰动容易导致系统传输功率的不稳定。主要针对移动负载供电时外部扰动带来的互感扰动问题,设计了一种适用于参数动态扰动下的IPT系统改进型鲁棒控制方法。借助线性分式变换,结合标称IPT系统广义状态空间平均模型及其参数的扰动特征,用含摄动反馈的线性动力学模型表征系统扰动模型;同时跟据广义混合灵敏度指标,计算基于系统扰动模型及目标传递函数的改进型H_∞鲁棒控制器;仿真及实验结果表明,所设计的鲁棒控制策略具有对输出电压的快速跟踪控制能力,且对参数扰动影响具有较好的抑制作用。展开更多
The Cryogenian Period was first established in 1988 along with other Precambrian eon,era and period-level subdivisions that were defined numerically by Global Standard Stratigraphic Ages(GSSAs).As absolute age constra...The Cryogenian Period was first established in 1988 along with other Precambrian eon,era and period-level subdivisions that were defined numerically by Global Standard Stratigraphic Ages(GSSAs).As absolute age constraints have improved,some of these time intervals no longer bracket adequately the geological event(s),for which they were named.For example,the age discrepancy between the basal Cryogenian GSSA at 850 Ma and the onset of widespread glaciation ca.展开更多
因负载变化、磁路机构的偏移以及元器件的老化等因素导致的双LCL型感应电能传输(inductively power transfer,IPT)系统出现输出电压变化及系统频率漂移等不确定性问题会加剧系统性能的恶化,为此,针对双LCL型IPT系统在负载摄动和干扰下...因负载变化、磁路机构的偏移以及元器件的老化等因素导致的双LCL型感应电能传输(inductively power transfer,IPT)系统出现输出电压变化及系统频率漂移等不确定性问题会加剧系统性能的恶化,为此,针对双LCL型IPT系统在负载摄动和干扰下的稳压输出,设计闭环系统的鲁棒控制器。首先采用广义状态空间平均法建立系统频域模型,将实际被控对象的模型转化为广义系统,借助上线性分式变换分离系统的标称部分和不确定部分,得到广义被控对象模型。然后,基于该模型设计H_∞鲁棒控制器,并利用结构奇异值的频率响应校验闭环系统的鲁棒稳定性及鲁棒性能。仿真和实验结果表明该控制器可以较好地保证双LCL型IPT系统的标称性能和鲁棒性能,验证了该模型和控制方法的有效性和可行性。展开更多
文摘The base of the ICS(International Commission on Stratigraphy)Geological Time Scale was ratified in 2022 by defining a new Global Stratigraphic Standard Age(GSSA)for the lower boundary of the Hadean Eon(formerly 4000–3600 Ma);the age of the Solar System based on the oldest solids,calcium-aluminium inclusions(CAIs),generated in the protoplanetary disk.The formal GSSA for the Hadean base is the oldest reliable,weighted mean Ucorrected Pb–Pb age of 4567.30±0.16 Ma obtained for CAIs in primitive meteorites Allende and Efremovka.This age is supported by the 4568–4567 Ma U-corrected Pb–Pb ages of chondrules in Northwest African meteorites.The boundary sets an upper lifetime for the protoplanetary disk and timing of planet formation.
文摘The Anthropocene as a prospective new,ongoing series/epoch must be defensible against all relevant concerns.We address the seven,still-relevant challenges posed to the Anthropocene Working Group by the Chair,International Commission on Stratigraphy(ICS),in 2014.(1)Concept or reality?The Anthropocene possesses a substantial,sharply distinctive stratigraphic record recognisable through many proxy signals from the mid-20th century onwards;(2)GSSP or GSSA?The Anthropocene can be defined by a GSSP and correlated globally;(3)Past or future?The Anthropocene unquestionably represents geological time,its transformations having already moved the Earth System beyond Holocene norms towards an irreversible future trajectory;(4)Utility?The Anthropocene’s distinctive material content allows useful delineation on geological sections/maps;(5)Indelibility?Many of the Anthropocene’s transformative effects cannot be subsequently effaced or overprinted;(6)Fit within the Geological Time Scale(GTS)?The Anthropocene represents a unique,youngest,interval in Earth history and strata of profound significance;(7)What is its value?The chronostratigraphic Anthropocene has conceptual usefulness even informally,but would then lack the clarity,stability and recognition that formalization provides.Without its formalization,the GTS would no longer accurately reflect Earth history,diminishing the relevance of geological science for analysis of ongoing planetary change.
文摘CLC谐振型感应电能传输系统较传统的LC谐振型系统具有更大的谐振容量和更小的频率漂移,但由于系统的高阶及多周期点特性,对CLC型系统的控制更为困难。为实现CLC谐振型系统的输出鲁棒控制,将系统状态变量及非线性开关函数进行频域线性化,通过平衡点变换,得到平衡点附近的广义状态空间平均(generalized state space averaging,GSSA)扰动模型。建立了系统的H∞控制系统结构,提出GSSA模型误差扰动有界定理并给出了证明。给出了相应的H∞扰动控制律,并通过仿真及实验结果验证了该模型及控制方法的有效性。
文摘在型谐振感应电能传输(inductive power transfer,IPT)系统中,由于负载及耦合参数变化,导致系统谐振频率产生随机漂移。针对频率不确定条件下的输出控制,利用广义状态空间平均(generalized state space averaging,GSSA)法对系统进行频域建模,将状态变量进行频域展开获得广义状态变量,从而获得线性状态空间模型。借助线性分式变换,将GSSA模型的确定部分与不确定部分分离,从而将系统的不确定模型转化为含摄动反馈的线性动力学系统。在此基础上提出一种基于GSSA模型的H_∞控制方法,又基于频域设计出混合灵敏度H_∞控制器,实现了多变量无静差跟踪鲁棒控制,并利用结构奇异值分析方法校验了鲁棒控制器的稳定性及性能。仿真及实验结果验证了其可行性。
文摘感应电能传输(inductive power transfer,IPT)技术应用于移动负载供电时,由于其能量传输的方向性限制,不可避免的振动、偏转等机械扰动容易导致系统传输功率的不稳定。主要针对移动负载供电时外部扰动带来的互感扰动问题,设计了一种适用于参数动态扰动下的IPT系统改进型鲁棒控制方法。借助线性分式变换,结合标称IPT系统广义状态空间平均模型及其参数的扰动特征,用含摄动反馈的线性动力学模型表征系统扰动模型;同时跟据广义混合灵敏度指标,计算基于系统扰动模型及目标传递函数的改进型H_∞鲁棒控制器;仿真及实验结果表明,所设计的鲁棒控制策略具有对输出电压的快速跟踪控制能力,且对参数扰动影响具有较好的抑制作用。
文摘The Cryogenian Period was first established in 1988 along with other Precambrian eon,era and period-level subdivisions that were defined numerically by Global Standard Stratigraphic Ages(GSSAs).As absolute age constraints have improved,some of these time intervals no longer bracket adequately the geological event(s),for which they were named.For example,the age discrepancy between the basal Cryogenian GSSA at 850 Ma and the onset of widespread glaciation ca.
文摘因负载变化、磁路机构的偏移以及元器件的老化等因素导致的双LCL型感应电能传输(inductively power transfer,IPT)系统出现输出电压变化及系统频率漂移等不确定性问题会加剧系统性能的恶化,为此,针对双LCL型IPT系统在负载摄动和干扰下的稳压输出,设计闭环系统的鲁棒控制器。首先采用广义状态空间平均法建立系统频域模型,将实际被控对象的模型转化为广义系统,借助上线性分式变换分离系统的标称部分和不确定部分,得到广义被控对象模型。然后,基于该模型设计H_∞鲁棒控制器,并利用结构奇异值的频率响应校验闭环系统的鲁棒稳定性及鲁棒性能。仿真和实验结果表明该控制器可以较好地保证双LCL型IPT系统的标称性能和鲁棒性能,验证了该模型和控制方法的有效性和可行性。
