The worldwide space industry has entered a new space economy era.The question is how to develop in this new era?This paper tries to answer this question from two aspects:highly reliable and low-cost technology for acc...The worldwide space industry has entered a new space economy era.The question is how to develop in this new era?This paper tries to answer this question from two aspects:highly reliable and low-cost technology for access to space,and the cislunar economic zone.Firstly,the development requirement of the future space transportation system is discussed and the development path to enable high-reliability and a low cost of space transportation system is analyzed.Moreover,the concept of a routine space transportation system is proposed,upon which this paper gives some thoughts to the development of the cislunar economic zone thus embracing the new space economy era.展开更多
Terahertz(THz) frequency region, defined from0.1 to 10 THz, is an important frequency band for radio astronomy and atmospheric science. As NbN Superconductor-Insulator-Superconductor(SIS) mixers used for terahertz det...Terahertz(THz) frequency region, defined from0.1 to 10 THz, is an important frequency band for radio astronomy and atmospheric science. As NbN Superconductor-Insulator-Superconductor(SIS) mixers used for terahertz detection, which are studied by the Purple Mountain Observatory(PMO), Chinese Academy of Sciences(CAS), work at 8–10 K, and require condition of micro vibrations, its astronomical observation in aerospace is limited by suitable refrigeration method. 4 K high frequency pulse tube cryocooler developed by Key Laboratory of Space Energy Conversion Technologies(SECT), Technical Institute of Physics and Chemistry(TIPC), CAS, offers an opportunity for the application of SIS mixers. This article introduces the progress of the two-stage high frequency pulse tube cryocooler researched by TIPC. The cryocooler has reached a no load temperature of 4.5 K which is the lowest temperature for this kind of cryocooler reported so far. The successful coupling between the THz component and the high frequency pulse tube cryocooler lays a solid foundation for space detection in the terahertz band.展开更多
This paper studies the effect of high-speed rail(HSR)on urban economic growth using a panel data comprising 285 Chinese cities in 2007-2017.Combining the endogenous growth model with a difference-in-difference analysi...This paper studies the effect of high-speed rail(HSR)on urban economic growth using a panel data comprising 285 Chinese cities in 2007-2017.Combining the endogenous growth model with a difference-in-difference analysis,we extend the horse-mass theory to explain how China may use HSR to avoid the so-called middle-income trap.The paper also examines the efficient boundaries of HSR and simultaneously studies HSR timespace compression as well as the city neighboring ejfects on economic growth.It is found that HSRs efficient boundaries are within the range of 200-1,200 km for provincial capitals and 50-300 km for prefecture-level cities.HSR stimulates economic growth by approximately 0.6 percent,and the neighboring effect accounts for one-quarter of economic growth.Three policy implications are drawn:(i)China needs tofurther reduce the travel times between the inland provincial cities and Beijing,Shanghai or Guangzhou;(ii)China should build a denser HSR network to maximize its economic impact on the vast majority of cities;(Hi)China needs to develop some powerful economic growth centers in the inland areas to lead the development of their neighboring cities.展开更多
Developing efficient,stable and economical electrocatalyst for oxygen evolution reaction(OER)is a significant pathway to produce clean energy from water splitting.Herein,the promising and highly efficient porous CoCrF...Developing efficient,stable and economical electrocatalyst for oxygen evolution reaction(OER)is a significant pathway to produce clean energy from water splitting.Herein,the promising and highly efficient porous CoCrFeNiMo high entropy alloys(HEAs)were prepared by microwave sintering using Mg space holder.Owing to unique properties of high entropy alloys and abundant active surface area,the porous CoCrFeNiMo-20 Mg exhibits excellent catalytic performance and prominent electrochemical stability with a low overpotential of 220 mV to reach current density of 10 mA cm^(-2),a small Tafel slope of 59.0 mV dec^(-1) and long-term durability for 24 h in 1.0 M KOH.The results of microstructure and element states indicate that crystal defects,porous structure and villous hydroxides are the reasons for high OER performance of the CoCrFeNiMo.This work not only provides a new way to prepare electrocatalysts,but also proves the important application of high entropy alloys in functional materials.展开更多
文摘The worldwide space industry has entered a new space economy era.The question is how to develop in this new era?This paper tries to answer this question from two aspects:highly reliable and low-cost technology for access to space,and the cislunar economic zone.Firstly,the development requirement of the future space transportation system is discussed and the development path to enable high-reliability and a low cost of space transportation system is analyzed.Moreover,the concept of a routine space transportation system is proposed,upon which this paper gives some thoughts to the development of the cislunar economic zone thus embracing the new space economy era.
基金supported by Strategic Pioneer Program on Space Science, Chinese Academy of Sciences (XDA04074100)
文摘Terahertz(THz) frequency region, defined from0.1 to 10 THz, is an important frequency band for radio astronomy and atmospheric science. As NbN Superconductor-Insulator-Superconductor(SIS) mixers used for terahertz detection, which are studied by the Purple Mountain Observatory(PMO), Chinese Academy of Sciences(CAS), work at 8–10 K, and require condition of micro vibrations, its astronomical observation in aerospace is limited by suitable refrigeration method. 4 K high frequency pulse tube cryocooler developed by Key Laboratory of Space Energy Conversion Technologies(SECT), Technical Institute of Physics and Chemistry(TIPC), CAS, offers an opportunity for the application of SIS mixers. This article introduces the progress of the two-stage high frequency pulse tube cryocooler researched by TIPC. The cryocooler has reached a no load temperature of 4.5 K which is the lowest temperature for this kind of cryocooler reported so far. The successful coupling between the THz component and the high frequency pulse tube cryocooler lays a solid foundation for space detection in the terahertz band.
基金This research was fnancially supported by the National Social Science Foundation of China(No.18ZDA005)the National Natural Science Foundation of China(Nos.71673033 and 71573077).
文摘This paper studies the effect of high-speed rail(HSR)on urban economic growth using a panel data comprising 285 Chinese cities in 2007-2017.Combining the endogenous growth model with a difference-in-difference analysis,we extend the horse-mass theory to explain how China may use HSR to avoid the so-called middle-income trap.The paper also examines the efficient boundaries of HSR and simultaneously studies HSR timespace compression as well as the city neighboring ejfects on economic growth.It is found that HSRs efficient boundaries are within the range of 200-1,200 km for provincial capitals and 50-300 km for prefecture-level cities.HSR stimulates economic growth by approximately 0.6 percent,and the neighboring effect accounts for one-quarter of economic growth.Three policy implications are drawn:(i)China needs tofurther reduce the travel times between the inland provincial cities and Beijing,Shanghai or Guangzhou;(ii)China should build a denser HSR network to maximize its economic impact on the vast majority of cities;(Hi)China needs to develop some powerful economic growth centers in the inland areas to lead the development of their neighboring cities.
基金The authors gratefully acknowledge the financial support of the project from the National Natural Science Foundation of China(51862026)the Natural Science Foundation of Jiangxi Province(20202ACBL214011,20192ACBL21048)the Aeronautical Science Foundation of China(2017ZF56027)。
文摘Developing efficient,stable and economical electrocatalyst for oxygen evolution reaction(OER)is a significant pathway to produce clean energy from water splitting.Herein,the promising and highly efficient porous CoCrFeNiMo high entropy alloys(HEAs)were prepared by microwave sintering using Mg space holder.Owing to unique properties of high entropy alloys and abundant active surface area,the porous CoCrFeNiMo-20 Mg exhibits excellent catalytic performance and prominent electrochemical stability with a low overpotential of 220 mV to reach current density of 10 mA cm^(-2),a small Tafel slope of 59.0 mV dec^(-1) and long-term durability for 24 h in 1.0 M KOH.The results of microstructure and element states indicate that crystal defects,porous structure and villous hydroxides are the reasons for high OER performance of the CoCrFeNiMo.This work not only provides a new way to prepare electrocatalysts,but also proves the important application of high entropy alloys in functional materials.
