In spite of the numerous advances in the development of H_(2)and O_(2)evolutions upon water splitting,the separation of H_(2)from O_(2)still remains a severe challenge.Herein,the novel dual-functional nanocatalysts Pd...In spite of the numerous advances in the development of H_(2)and O_(2)evolutions upon water splitting,the separation of H_(2)from O_(2)still remains a severe challenge.Herein,the novel dual-functional nanocatalysts Pd/carbon nanosphere(CNS),obtained via immobilization of ultrafine Pd nanoparticles onto CNS,are developed and employed for both selective H_(2)generation from HCOOH dehydrogenation and O_(2)evolution from H_(2)O_(2)decomposition.In these reactions,the highest activities for Pd/CNS-800(i.e.,calcinated at 800℃)are 2478 h−1 and 993 min^(−1)for H_(2)and O_(2)evolution,respectively.The highly efficient and selective“on-off”switch for selective H_(2)generation from HCOOH is successfully realized by pH adjustment.This novel and highly efficient nanocatalyst Pd/CNS-800 not only provides new approaches for the promising application of HCOOH and H_(2)O_(2)as economic and safe H_(2)and O_(2)carriers,respectively,for fuel cells,but also promotes the development of“on-off”switch for on-demand H_(2)evolution.展开更多
This paper presents an asynchronous output-feed-back control strategy of semi-Markovian systems via sliding mode-based learning technique.Compared with most literature results that require exact prior knowledge of sys...This paper presents an asynchronous output-feed-back control strategy of semi-Markovian systems via sliding mode-based learning technique.Compared with most literature results that require exact prior knowledge of system state and mode information,an asynchronous output-feedback sliding sur-face is adopted in the case of incompletely available state and non-synchronization phenomenon.The holonomic dynamics of the sliding mode are characterized by a descriptor system in which the switching surface is regarded as the fast subsystem and the system dynamics are viewed as the slow subsystem.Based upon the co-occurrence of two subsystems,the sufficient stochastic admissibility criterion of the holonomic dynamics is derived by utilizing the characteristics of cumulative distribution functions.Furthermore,a recursive learning controller is formulated to guarantee the reachability of the sliding manifold and realize the chattering reduction of the asynchronous switching and sliding motion.Finally,the proposed theoretical method is substantia-ted through two numerical simulations with the practical contin-uous stirred tank reactor and F-404 aircraft engine model,respectively.展开更多
In this paper, we propose a dual-threshold based secure On-Off transmission scheme, where signals are transmitted only if the channel condition can guarantee secure and reliable communication. First, we present a dyna...In this paper, we propose a dual-threshold based secure On-Off transmission scheme, where signals are transmitted only if the channel condition can guarantee secure and reliable communication. First, we present a dynamic access strategy to increase access efficiency, which provides an access region for the intended user. Then, we propose an emission control policy to transmit signals according to the current channel condition, which declines the influence of channel estimation errors and guarantees qualities of communication links. Furthermore, we give a comprehensive performance analysis for the proposed scheme in terms of connection outage probability(COP) and secrecy outage probability(SOP), and present a dual-threshold optimization model to further support the performance. Numerical results verify that the secure On-Off transmission scheme can increase the system secure energy efficiency and guarantee reliable and secure communication.展开更多
Growth and passivation of tunnels within Al foil by on-off controlling DC etching in 6 wt.% HCI solution has been investigated. It was found that, in a given etchant solution at a special temperature, the longest tunn...Growth and passivation of tunnels within Al foil by on-off controlling DC etching in 6 wt.% HCI solution has been investigated. It was found that, in a given etchant solution at a special temperature, the longest tunnel length was only a function of the turn-on interval of DC. The potential of Al foil broke at on-off controlling DC by the result from anode polarization curves and potential-time (E-t) responding curves. When DC was switched on, the potential increased abruptly over pitting potential, leading to nucleation of pits at the surface and the growth of tunnels at special length. When DC was switched off, the potential decreased rapidly to a passive value, leading to stoppage of nucleation and death of tunnels. By this way, the longest tunnel length can be controlled and a non-piercing layer can be obtained. Hence, etching of Al foil at this current is beneficial for maintaining a good mechanical strength.展开更多
To improve the switching time of the control force in standard sky-hook ON-OFF semi-active control algorithm,a stateadjust coefficient was adopted in the improved ON-OFF( ION-OFF)algorithm. In considering of the ridin...To improve the switching time of the control force in standard sky-hook ON-OFF semi-active control algorithm,a stateadjust coefficient was adopted in the improved ON-OFF( ION-OFF)algorithm. In considering of the riding comfort and the handling stability of vehicle, a comprehensive performance assessment criterion on suspension system was established with the utilization of the corresponding passive suspension system. Several simulations and analyses were conducted on improved ON-OFF semi-active suspension system with the comparison of passive suspension system and ON-OFF semi-active suspension system. The simulation results showed that the optimal comprehensive performance of the improved ON-OFF suspension system could be achieved when the state-adjust coefficient equalled 0. 6 as the vehicle running on C level road with the speed of 10 m/s,and the comprehensive performance was better than ON-OFF suspension system. Conclusions could be drawn from the frequency domain analysis that the performance of riding comfort and handling stability were both improved in the low resonance frequency and the mid-frequency range. The fact could be known that the comprehensive performance of the suspension system was associated with the frequency of the riding road and the sprung mass( SM) with the analysis of affecting factors.展开更多
According to the valve port features of high speed on-off valve and its actions, the valve port can be simplified into an a-type half bridge construction. A method that tests the dynamic characteristics of the high sp...According to the valve port features of high speed on-off valve and its actions, the valve port can be simplified into an a-type half bridge construction. A method that tests the dynamic characteristics of the high speed on-off valve by the output pressure signal of the a-type half bridge is proposed. Having analyzed the factors related to the dynamic characteristics of an a-type half bridge, a rule for designing the outlet chamber's volume is worked out. According to the rule, a test stand is built to test the self-developed high-speed on-off valve. From the test results, it can be seen that with the outlet chamber's volume controlled by the rule the rise time of the pressure signals driven by signals with different frequencies changes very little. The test results conform to the simulation results, which nroves the correctness of the method.展开更多
基金National Natural Science Foundation of China,Grant/Award Number:21805166111 Project of China,Grant/Award Number:D20015+1 种基金Ministryof Education,Hubei province,China,Grant/Award Number:T2020004Foundation of Science and Technology Bureau of Yichang City,Grant/Award Number:A21‐3‐012。
文摘In spite of the numerous advances in the development of H_(2)and O_(2)evolutions upon water splitting,the separation of H_(2)from O_(2)still remains a severe challenge.Herein,the novel dual-functional nanocatalysts Pd/carbon nanosphere(CNS),obtained via immobilization of ultrafine Pd nanoparticles onto CNS,are developed and employed for both selective H_(2)generation from HCOOH dehydrogenation and O_(2)evolution from H_(2)O_(2)decomposition.In these reactions,the highest activities for Pd/CNS-800(i.e.,calcinated at 800℃)are 2478 h−1 and 993 min^(−1)for H_(2)and O_(2)evolution,respectively.The highly efficient and selective“on-off”switch for selective H_(2)generation from HCOOH is successfully realized by pH adjustment.This novel and highly efficient nanocatalyst Pd/CNS-800 not only provides new approaches for the promising application of HCOOH and H_(2)O_(2)as economic and safe H_(2)and O_(2)carriers,respectively,for fuel cells,but also promotes the development of“on-off”switch for on-demand H_(2)evolution.
基金supported in part by the National Science Fund for Excellent Young Scholars of China(62222317)the National Science Foundation of China(62303492)+3 种基金the Major Science and Technology Projects in Hunan Province(2021GK1030)the Science and Technology Innovation Program of Hunan Province(2022WZ1001)the Key Research and Development Program of Hunan Province(2023GK2023)the Fundamental Research Funds for the Central Universities of Central South University(2024ZZTS0116)。
文摘This paper presents an asynchronous output-feed-back control strategy of semi-Markovian systems via sliding mode-based learning technique.Compared with most literature results that require exact prior knowledge of system state and mode information,an asynchronous output-feedback sliding sur-face is adopted in the case of incompletely available state and non-synchronization phenomenon.The holonomic dynamics of the sliding mode are characterized by a descriptor system in which the switching surface is regarded as the fast subsystem and the system dynamics are viewed as the slow subsystem.Based upon the co-occurrence of two subsystems,the sufficient stochastic admissibility criterion of the holonomic dynamics is derived by utilizing the characteristics of cumulative distribution functions.Furthermore,a recursive learning controller is formulated to guarantee the reachability of the sliding manifold and realize the chattering reduction of the asynchronous switching and sliding motion.Finally,the proposed theoretical method is substantia-ted through two numerical simulations with the practical contin-uous stirred tank reactor and F-404 aircraft engine model,respectively.
基金supported in part by National Natural Science Foundation of China under Grants No. 61871404, 61401510, 61521003, 61501516
文摘In this paper, we propose a dual-threshold based secure On-Off transmission scheme, where signals are transmitted only if the channel condition can guarantee secure and reliable communication. First, we present a dynamic access strategy to increase access efficiency, which provides an access region for the intended user. Then, we propose an emission control policy to transmit signals according to the current channel condition, which declines the influence of channel estimation errors and guarantees qualities of communication links. Furthermore, we give a comprehensive performance analysis for the proposed scheme in terms of connection outage probability(COP) and secrecy outage probability(SOP), and present a dual-threshold optimization model to further support the performance. Numerical results verify that the secure On-Off transmission scheme can increase the system secure energy efficiency and guarantee reliable and secure communication.
基金This study was financially supported by Beijing Education Commission,China.
文摘Growth and passivation of tunnels within Al foil by on-off controlling DC etching in 6 wt.% HCI solution has been investigated. It was found that, in a given etchant solution at a special temperature, the longest tunnel length was only a function of the turn-on interval of DC. The potential of Al foil broke at on-off controlling DC by the result from anode polarization curves and potential-time (E-t) responding curves. When DC was switched on, the potential increased abruptly over pitting potential, leading to nucleation of pits at the surface and the growth of tunnels at special length. When DC was switched off, the potential decreased rapidly to a passive value, leading to stoppage of nucleation and death of tunnels. By this way, the longest tunnel length can be controlled and a non-piercing layer can be obtained. Hence, etching of Al foil at this current is beneficial for maintaining a good mechanical strength.
基金Military Scientific Project,China(No.2013ZB06)Innovation Engineering Project of General Armament Department,China(No.2015YY04)
文摘To improve the switching time of the control force in standard sky-hook ON-OFF semi-active control algorithm,a stateadjust coefficient was adopted in the improved ON-OFF( ION-OFF)algorithm. In considering of the riding comfort and the handling stability of vehicle, a comprehensive performance assessment criterion on suspension system was established with the utilization of the corresponding passive suspension system. Several simulations and analyses were conducted on improved ON-OFF semi-active suspension system with the comparison of passive suspension system and ON-OFF semi-active suspension system. The simulation results showed that the optimal comprehensive performance of the improved ON-OFF suspension system could be achieved when the state-adjust coefficient equalled 0. 6 as the vehicle running on C level road with the speed of 10 m/s,and the comprehensive performance was better than ON-OFF suspension system. Conclusions could be drawn from the frequency domain analysis that the performance of riding comfort and handling stability were both improved in the low resonance frequency and the mid-frequency range. The fact could be known that the comprehensive performance of the suspension system was associated with the frequency of the riding road and the sprung mass( SM) with the analysis of affecting factors.
文摘According to the valve port features of high speed on-off valve and its actions, the valve port can be simplified into an a-type half bridge construction. A method that tests the dynamic characteristics of the high speed on-off valve by the output pressure signal of the a-type half bridge is proposed. Having analyzed the factors related to the dynamic characteristics of an a-type half bridge, a rule for designing the outlet chamber's volume is worked out. According to the rule, a test stand is built to test the self-developed high-speed on-off valve. From the test results, it can be seen that with the outlet chamber's volume controlled by the rule the rise time of the pressure signals driven by signals with different frequencies changes very little. The test results conform to the simulation results, which nroves the correctness of the method.