Prussian blue analogues(PBA)possess a high theoretical specific capacity for sodium ion batteries.However,cycling PBA to a high current density causes severe capacity fading.Here,we develop a selective edge-etching ap...Prussian blue analogues(PBA)possess a high theoretical specific capacity for sodium ion batteries.However,cycling PBA to a high current density causes severe capacity fading.Here,we develop a selective edge-etching approach to tackle this long-standing issue of poor rate capability.Well-crystallized PBA particles were produced by hydrothermal treatment of a sodium hexacyanoferrate precursor dissolved in muriatic acid solution,which were then eroded in hydrochloric acid solution to promote selective etching along the edges of the PBA crystals.The defect concentration([Fe(CN)_(6)]^(4-))on the edge is denser than that at the face or corner,which stimulates the preferred etching of edges via the defect-induced heterogeneous mechanism.Due to the increasing exposed surface area and active sites,the etched PBA display much improved electrochemical performance with a capacity of 167 mA h g^(-1) at a current density of 5 mA g^(-1) and a capacity retention of 82.7%when the current density was increased to 40 mA g^(-1),demonstrating fast sodium ion transfer and high rate capability.展开更多
Exoatmospheric intercept plays a crucial role in strategic defense.However,existing approaches for exoatmospheric intercept guidance primarily rely on either proportional navigation or Lambert’s problem solution,whic...Exoatmospheric intercept plays a crucial role in strategic defense.However,existing approaches for exoatmospheric intercept guidance primarily rely on either proportional navigation or Lambert’s problem solution,which needs continuous relative measurements or requires constant orbit corrections due to its sensitivity to perturbation forces.To address these limitations,this paper proposes a novel guidance scheme based on relative-motion control.First,by introducing the zero-effort orbit as a reference orbit,the intercept problem is transformed into an equivalent relative-motion control problem with respect to the zero-effort orbit.The relative-motion dynamics model is adopted to analytically solve the velocity-to-be-gained vector,which avoids the iterative computation in the Lambert routine.Then,the guidance scheme is established,which generates a command thrust vector aligned with the velocity-to-be-gained vector in each guidance period.Through feedback control,the desired velocity is incrementally achieved until the velocity-to-be-gained vector becomes zero,ensuring accurate interception.Compared with the existing exoatmospheric intercept guidance methods,the presented method improves 1 or 2 orders of guidance accuracy in the low-Earth orbit intercept mission and 3 orders of guidance accuracy in the high-Earth orbit intercept mission,which are practical options for engineering applications.展开更多
基金financially supported by the Basic Research Project of the Science and Technology Innovation Commission of Shenzhen(No.JCYJ20170412153139454 and No.JCYJ20170817110251498)the Guangdong Special Support for the Science and Technology Leading Young Scientist(No.2016TQ03C919)+1 种基金the National Natural Science Foundation of China(No.21875097,No.21671096 and No.21603094)the Guangdong Innovative and Entrepreneurial Research Team Program(No.2016ZT06G587).
文摘Prussian blue analogues(PBA)possess a high theoretical specific capacity for sodium ion batteries.However,cycling PBA to a high current density causes severe capacity fading.Here,we develop a selective edge-etching approach to tackle this long-standing issue of poor rate capability.Well-crystallized PBA particles were produced by hydrothermal treatment of a sodium hexacyanoferrate precursor dissolved in muriatic acid solution,which were then eroded in hydrochloric acid solution to promote selective etching along the edges of the PBA crystals.The defect concentration([Fe(CN)_(6)]^(4-))on the edge is denser than that at the face or corner,which stimulates the preferred etching of edges via the defect-induced heterogeneous mechanism.Due to the increasing exposed surface area and active sites,the etched PBA display much improved electrochemical performance with a capacity of 167 mA h g^(-1) at a current density of 5 mA g^(-1) and a capacity retention of 82.7%when the current density was increased to 40 mA g^(-1),demonstrating fast sodium ion transfer and high rate capability.
文摘Exoatmospheric intercept plays a crucial role in strategic defense.However,existing approaches for exoatmospheric intercept guidance primarily rely on either proportional navigation or Lambert’s problem solution,which needs continuous relative measurements or requires constant orbit corrections due to its sensitivity to perturbation forces.To address these limitations,this paper proposes a novel guidance scheme based on relative-motion control.First,by introducing the zero-effort orbit as a reference orbit,the intercept problem is transformed into an equivalent relative-motion control problem with respect to the zero-effort orbit.The relative-motion dynamics model is adopted to analytically solve the velocity-to-be-gained vector,which avoids the iterative computation in the Lambert routine.Then,the guidance scheme is established,which generates a command thrust vector aligned with the velocity-to-be-gained vector in each guidance period.Through feedback control,the desired velocity is incrementally achieved until the velocity-to-be-gained vector becomes zero,ensuring accurate interception.Compared with the existing exoatmospheric intercept guidance methods,the presented method improves 1 or 2 orders of guidance accuracy in the low-Earth orbit intercept mission and 3 orders of guidance accuracy in the high-Earth orbit intercept mission,which are practical options for engineering applications.
