To solve the problem of multi-target hunting by an unmanned surface vehicle(USV)fleet,a hunting algorithm based on multi-agent reinforcement learning is proposed.Firstly,the hunting environment and kinematic model wit...To solve the problem of multi-target hunting by an unmanned surface vehicle(USV)fleet,a hunting algorithm based on multi-agent reinforcement learning is proposed.Firstly,the hunting environment and kinematic model without boundary constraints are built,and the criteria for successful target capture are given.Then,the cooperative hunting problem of a USV fleet is modeled as a decentralized partially observable Markov decision process(Dec-POMDP),and a distributed partially observable multitarget hunting Proximal Policy Optimization(DPOMH-PPO)algorithm applicable to USVs is proposed.In addition,an observation model,a reward function and the action space applicable to multi-target hunting tasks are designed.To deal with the dynamic change of observational feature dimension input by partially observable systems,a feature embedding block is proposed.By combining the two feature compression methods of column-wise max pooling(CMP)and column-wise average-pooling(CAP),observational feature encoding is established.Finally,the centralized training and decentralized execution framework is adopted to complete the training of hunting strategy.Each USV in the fleet shares the same policy and perform actions independently.Simulation experiments have verified the effectiveness of the DPOMH-PPO algorithm in the test scenarios with different numbers of USVs.Moreover,the advantages of the proposed model are comprehensively analyzed from the aspects of algorithm performance,migration effect in task scenarios and self-organization capability after being damaged,the potential deployment and application of DPOMH-PPO in the real environment is verified.展开更多
Regulating the local coordination of Fe active center can further improve the oxygen reduction reaction(ORR)performance of Fe-N-C catalyst to meet the practical application requirements of zinc-air batteries(ZABs).Her...Regulating the local coordination of Fe active center can further improve the oxygen reduction reaction(ORR)performance of Fe-N-C catalyst to meet the practical application requirements of zinc-air batteries(ZABs).Herein,carbon vacancies modified hollow porous catalysts(C-FeZ8@PDA-950)are constructed by microenvironment modulation,achieving the efficient utilization of active sites and optimization of elec-tronic structure.Density functional theory(DFT)calculations confirm that the defective-edge Fe-N_(4) sites can weaken the adsorption free energy of OH^(∗),and hinder the dissolution of Fe center,significantly accel-erating the ORR process for ZABs.The rechargeable liquid ZABs equipped with C-FeZ8@PDA-950 display high specific capacity(819.95 mAh g Zn^(−1))and excellent long-cycling life(over 500 h).Furthermore,the relevant flexible all-solid-state ZABs also display outstanding folding performance under various bending angles.This work will provide insights into optimizing the electronic structure to improve electrocatalytic performance in the energy conversion and storage area.展开更多
Developing efficient transition metal-nitrogen-carbon(TM-N-C)catalysts with abundant accessible active sites has been in the limelight in recent years due to their exceptional application potential in Zn-air bat-terie...Developing efficient transition metal-nitrogen-carbon(TM-N-C)catalysts with abundant accessible active sites has been in the limelight in recent years due to their exceptional application potential in Zn-air bat-teries(ZABs).Herein,we report the simple and environmentally-friendly fabrication of a single-atom Co electrocatalyst,Co-SA/N-C_(900),via in-suit pyrolysis of the co-precursor containing sucrose,dicyandiamide,and Co salts.The Co single atoms coordinated with adjacent N atoms are anchored on the doped ordered mesoporous carbon,generating the atomic Co-N_(4)moiety.Co-SA/N-C_(900)displays high oxygen reduction reaction(ORR)activity with an onset potential of 0.96 V and a half-wave potential of 0.87 V.Notably,the liquid ZAB with Co-SA/N-C_(900)catalyst exhibits exceptional discharge specific capacity of 706.38 mAh g^(-1),peak power density of 191.11 mW cm^(-2),and excellent stability at high current densities up to 100 mA cm^(-2),surpassing commercial Pt/C.According to the density functional theory(DFT)study,the Co-N_(4)moi-ety with graphitic N dopants can decrease the rate-determining step(RDS)energy barrier and thus accel-erate the ORR process.This study offers experimental and theoretical guidelines for the rational design of TM-N-C catalysts for practical implementation with notable ORR activity for application in ZABs.展开更多
Photocatalysis using polymeric carbon nitride(CN)materials is a constantly evolving field,where the variation of synthetic procedures allows the constant improvement of activity by tackling the intrinsic limitations o...Photocatalysis using polymeric carbon nitride(CN)materials is a constantly evolving field,where the variation of synthetic procedures allows the constant improvement of activity by tackling the intrinsic limitations of these materials(optical absorbance,specific surface area,charge migration,etc.).Amongst the possible photocatalytic reactions,the most popular application of CNs is the hydrogen evolution reaction(HER)from water.In this work,we design precisely-controlled carbon-doped porous CN rods with extended π-electron conjugation from supramolecular assemblies of melem and co-monomers,which partially substitute nitrogen for carbon atoms at the pyrimidine ring of the melem.Dense hydrogen bonds and good thermal stability of the melem-based supramolecular framework allow synthesizing a more ordered structure for improved charge migration;the control from the molecular level over the position of carbon-substituted nitrogen positions tailors the band alignment and photogenerated charge separation.The optimal photocatalyst shows an excellent HER rate(up to 10.16 mmol·h-1·g-1 under 100 W white light-emitting diode(LED)irradiation,with an apparent quantum efficiency of 20.0%at 405 nm,which is 23.2 times higher compared to a reference bulk CN).To fully harness the benefits of the developed metal-free CNs,selective oxidation reaction of aromatic alcohols is demonstrated with high conversion and selectivity.展开更多
This paper builds a theoretical framework of two-period general equilibrium model to explore whether 1) the restrictions of the Islamic financial system(RIFS) limit economic development in Xinjiang and 2) counterpart ...This paper builds a theoretical framework of two-period general equilibrium model to explore whether 1) the restrictions of the Islamic financial system(RIFS) limit economic development in Xinjiang and 2) counterpart financial support for Xinjiang(CFSX) promotes economic development and social stability. First, we introduce above mentioned restrictions caused by Islamic beliefs into a general equilibrium model and modify Islamic agents' budget constraints to define the benchmark equilibrium.Comparing the benchmark equilibrium with the perfect equilibrium, in which these restrictions are removed, we discover the RIFS paradox that RIFS undermine the social welfare and income of Muslims.Second, the financial support is introduced into the pattern of benchmark equilibrium as an exogenous variable to model its impact and hence we define the CFSX equilibrium. A series of policy analyses implies that the CFSX strategy improves living standards and social welfare in Xinjiang.展开更多
基金financial support from National Natural Science Foundation of China(Grant No.61601491)Natural Science Foundation of Hubei Province,China(Grant No.2018CFC865)Military Research Project of China(-Grant No.YJ2020B117)。
文摘To solve the problem of multi-target hunting by an unmanned surface vehicle(USV)fleet,a hunting algorithm based on multi-agent reinforcement learning is proposed.Firstly,the hunting environment and kinematic model without boundary constraints are built,and the criteria for successful target capture are given.Then,the cooperative hunting problem of a USV fleet is modeled as a decentralized partially observable Markov decision process(Dec-POMDP),and a distributed partially observable multitarget hunting Proximal Policy Optimization(DPOMH-PPO)algorithm applicable to USVs is proposed.In addition,an observation model,a reward function and the action space applicable to multi-target hunting tasks are designed.To deal with the dynamic change of observational feature dimension input by partially observable systems,a feature embedding block is proposed.By combining the two feature compression methods of column-wise max pooling(CMP)and column-wise average-pooling(CAP),observational feature encoding is established.Finally,the centralized training and decentralized execution framework is adopted to complete the training of hunting strategy.Each USV in the fleet shares the same policy and perform actions independently.Simulation experiments have verified the effectiveness of the DPOMH-PPO algorithm in the test scenarios with different numbers of USVs.Moreover,the advantages of the proposed model are comprehensively analyzed from the aspects of algorithm performance,migration effect in task scenarios and self-organization capability after being damaged,the potential deployment and application of DPOMH-PPO in the real environment is verified.
基金supported by the National Natural Science Foundation of China(Nos.22078028,21978026,22209016)the International Scientific and Technological Cooperation Program of Changzhou(No.CZ20220028)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX23_3025).
文摘Regulating the local coordination of Fe active center can further improve the oxygen reduction reaction(ORR)performance of Fe-N-C catalyst to meet the practical application requirements of zinc-air batteries(ZABs).Herein,carbon vacancies modified hollow porous catalysts(C-FeZ8@PDA-950)are constructed by microenvironment modulation,achieving the efficient utilization of active sites and optimization of elec-tronic structure.Density functional theory(DFT)calculations confirm that the defective-edge Fe-N_(4) sites can weaken the adsorption free energy of OH^(∗),and hinder the dissolution of Fe center,significantly accel-erating the ORR process for ZABs.The rechargeable liquid ZABs equipped with C-FeZ8@PDA-950 display high specific capacity(819.95 mAh g Zn^(−1))and excellent long-cycling life(over 500 h).Furthermore,the relevant flexible all-solid-state ZABs also display outstanding folding performance under various bending angles.This work will provide insights into optimizing the electronic structure to improve electrocatalytic performance in the energy conversion and storage area.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.22078028 and 21978026).
文摘Developing efficient transition metal-nitrogen-carbon(TM-N-C)catalysts with abundant accessible active sites has been in the limelight in recent years due to their exceptional application potential in Zn-air bat-teries(ZABs).Herein,we report the simple and environmentally-friendly fabrication of a single-atom Co electrocatalyst,Co-SA/N-C_(900),via in-suit pyrolysis of the co-precursor containing sucrose,dicyandiamide,and Co salts.The Co single atoms coordinated with adjacent N atoms are anchored on the doped ordered mesoporous carbon,generating the atomic Co-N_(4)moiety.Co-SA/N-C_(900)displays high oxygen reduction reaction(ORR)activity with an onset potential of 0.96 V and a half-wave potential of 0.87 V.Notably,the liquid ZAB with Co-SA/N-C_(900)catalyst exhibits exceptional discharge specific capacity of 706.38 mAh g^(-1),peak power density of 191.11 mW cm^(-2),and excellent stability at high current densities up to 100 mA cm^(-2),surpassing commercial Pt/C.According to the density functional theory(DFT)study,the Co-N_(4)moi-ety with graphitic N dopants can decrease the rate-determining step(RDS)energy barrier and thus accel-erate the ORR process.This study offers experimental and theoretical guidelines for the rational design of TM-N-C catalysts for practical implementation with notable ORR activity for application in ZABs.
基金grateful for the financial support from the National Natural Science Foundation of China(Nos.22078028 and 21978026)the Special Program for Introducing Foreign Talents of Changzhou(No.CQ20214032)+1 种基金the joint Israel Science Foundation-National Science Foundation of China(ISF-NSFC)(No.2969/19 and the ISF No.601/21)The authors thank Jonathan Tzadikov,Rotem Geva,Liel Abisdris,Junyi Li,and Ayelet Tashakory(Ben-Gurion University of the Negev)for technical support and Dr.Laurent Chabanne for fruitful discussion.
文摘Photocatalysis using polymeric carbon nitride(CN)materials is a constantly evolving field,where the variation of synthetic procedures allows the constant improvement of activity by tackling the intrinsic limitations of these materials(optical absorbance,specific surface area,charge migration,etc.).Amongst the possible photocatalytic reactions,the most popular application of CNs is the hydrogen evolution reaction(HER)from water.In this work,we design precisely-controlled carbon-doped porous CN rods with extended π-electron conjugation from supramolecular assemblies of melem and co-monomers,which partially substitute nitrogen for carbon atoms at the pyrimidine ring of the melem.Dense hydrogen bonds and good thermal stability of the melem-based supramolecular framework allow synthesizing a more ordered structure for improved charge migration;the control from the molecular level over the position of carbon-substituted nitrogen positions tailors the band alignment and photogenerated charge separation.The optimal photocatalyst shows an excellent HER rate(up to 10.16 mmol·h-1·g-1 under 100 W white light-emitting diode(LED)irradiation,with an apparent quantum efficiency of 20.0%at 405 nm,which is 23.2 times higher compared to a reference bulk CN).To fully harness the benefits of the developed metal-free CNs,selective oxidation reaction of aromatic alcohols is demonstrated with high conversion and selectivity.
基金the National Natural Science Foundation of China(71573220,71773123)。
文摘This paper builds a theoretical framework of two-period general equilibrium model to explore whether 1) the restrictions of the Islamic financial system(RIFS) limit economic development in Xinjiang and 2) counterpart financial support for Xinjiang(CFSX) promotes economic development and social stability. First, we introduce above mentioned restrictions caused by Islamic beliefs into a general equilibrium model and modify Islamic agents' budget constraints to define the benchmark equilibrium.Comparing the benchmark equilibrium with the perfect equilibrium, in which these restrictions are removed, we discover the RIFS paradox that RIFS undermine the social welfare and income of Muslims.Second, the financial support is introduced into the pattern of benchmark equilibrium as an exogenous variable to model its impact and hence we define the CFSX equilibrium. A series of policy analyses implies that the CFSX strategy improves living standards and social welfare in Xinjiang.
