This paper reports on the time and frequency standard system for the Five-hundred meter Aperture Spherical radio Telescope(FAST),including the system design,stability measurements and pulsar timing observations.The st...This paper reports on the time and frequency standard system for the Five-hundred meter Aperture Spherical radio Telescope(FAST),including the system design,stability measurements and pulsar timing observations.The stability and drift rate of the frequency standard are calculated using 1-year monitoring data.The UTC-NIM Disciplined Oscillator(NIMDO)system improves the system time accuracy and stability to the level of 5 ns.Pulsar timing observations were carried out for several months.The weighted RMS of timing residuals reaches the level of less than 3.0μs.展开更多
A strategy for copper-catalyzed and biphosphine ligand controlled boracarboxylation of 1,3-dienes and CO_(2) with 3,4-selectivity was developed.The Cu Cl coupled with DPPF(1,1-bis(diphenylphosphino)ferrocene)was assig...A strategy for copper-catalyzed and biphosphine ligand controlled boracarboxylation of 1,3-dienes and CO_(2) with 3,4-selectivity was developed.The Cu Cl coupled with DPPF(1,1-bis(diphenylphosphino)ferrocene)was assigned to be the best catalyst,with 84%yield and exclusive3,4-selectivity.The ligand effect on both catalytic activity and regioselectivity of boracarboxylation was disclosed,which is rarely reported in any copper catalyzed boracarboxylation.The borocupration process is revealed to be a vital step for the biphosphine participated boracarboxylation of 1,3-dienes with CO_(2).The minimal substrate distortion occurring in 3,4-borocupration favors the 3,4-regioselectivity of boracarboxylation.The“pocket”confinement and suitableβ_(n)(92°–106°)of bisphosphine ligands are demonstrated to be in favour of the interaction between LCu-Bpin complex(the catalytic precursor)and1,3-diene substrate to decrease their interaction energyΔE_(int)(ζ)in 3,4-borocupration,thus promoting the 3,4-boracarboxylation.展开更多
Against the strategic backdrop of forging and strengthening the consciousness of the Chinese national community in the new era,universities in border areas,as crucial platforms for the integration of multi-ethnic cult...Against the strategic backdrop of forging and strengthening the consciousness of the Chinese national community in the new era,universities in border areas,as crucial platforms for the integration of multi-ethnic cultures,shoulder the significant mission of enhancing ethnic unity and promoting outstanding traditional Chinese culture.As an important carrier of Chinese culture,ethnic music not only contains profound historical memories and emotional identities but also demonstrates a powerful cultural and educational function in the teaching of border universities.Based on the actual situation of universities in border areas,this paper analyzes the unique value of ethnic music in cultivating students’national identity,cultural identity,and emotional identity,and explores effective paths for it to empower the forging and strengthening of the consciousness of the Chinese national community in teaching practice.By combining policy orientations and teaching status quo,the paper points out the main dilemmas such as single curriculum content,insufficient integration of ideological and political education,and a lack of practical resources,and proposes countermeasures such as strengthening the integration of ideological and political education,optimizing the curriculum structure,and expanding practical platforms.Through the deepening and innovation of ethnic music education,border universities can effectively enhance students’cultural consciousness and cultural confidence,providing solid educational support for forging and strengthening the consciousness of the Chinese national community.This paper has positive significance for promoting the high-quality development of education in border universities and constructing a new-era ethnic unity and progress education system.展开更多
Constructing a valid heterointerface with a built-in electric field is an effective strategy for designing energy storage anodes with exceptional efficiency for potassium-ion batteries(PIBs)and sodium-ion batteries(SI...Constructing a valid heterointerface with a built-in electric field is an effective strategy for designing energy storage anodes with exceptional efficiency for potassium-ion batteries(PIBs)and sodium-ion batteries(SIBs).In this study,WSe_(2)/MoSe_(2)nanosheets with a better-matched and stable heterojunction interface were uniformly embedded in carbon nanofiber frameworks(WSe_(2)/MoSe_(2)/CNFs).The ion/electron transfer kinetics were facilitated by heterointerfaces with an enlarged effective utilization range.Meanwhile,the heterointerface directed electron transfer from MoSe_(2)to WSe_(2)and had significant potassium adsorption capability.The ultra-high pseudocapacitance contribution originating from the heterostructure and morphological features of the WSe_(2)/MoSe_(2)nanosheets contributed to enhancing high-rate energy storage.Moreover,in situ X-ray diffraction and ex situ X-ray photoelectron spectroscopy revealed the potassification/depotassification behavior of the WSe_(2)/MoSe_(2)/CNFs during the conversion reaction.Consequently,after 500 cycles at 5 A·g^(-1),the WSe_(2)/MoSe_(2)/CNF anode demonstrated an outstanding long-term cycling performance of 125.6 mAh·g^(-1)for PIBs.While serving as a SIB electrode,it exhibited an exceptional rate capability of 243.5 mAh·g^(-1)at 20 A·g^(-1).With the goal of developing high-performance PIB/SIB electrode materials,the proposed strategy,based on heterointerface adaptation engineering,is promising.展开更多
In this study,we explored a one-step direct synthesis of NH3 under mild experimental conditions utilizing pulse-modulated microwave plasma technology at atmospheric pressure.At a substantial gas flow rate,a microwave ...In this study,we explored a one-step direct synthesis of NH3 under mild experimental conditions utilizing pulse-modulated microwave plasma technology at atmospheric pressure.At a substantial gas flow rate,a microwave plasma jet was formed and the microwave-assisted ammonia synthesis can be realized.Impacts of various parameters including the gas flow rate,gas component,microwave absorbed power,pulse modulation frequency,and pulse duty cycle on ammonia synthesis were systematically investigated.To indicate the reaction path of ammonia synthesis,the distributions of both the gas temperature and active species were also studied using optical emission spectra technology.It is found that a considerable amount of ammonia was directly synthesized without involvement of any catalysts,the highest ammonia production rate and energy efficiency(EE),up to 2.93μmol·min^(-1) and 6.64×10^(-2)g·(k W·h)^(-1),respectively,were achieved under low microwave power of 84.42 W.The duty cycle has obvious influences on the synthesis efficiency,compared to a duty cycle of 80%,the ammonia synthesis rate,EE and nitrogen conversion decreased by about 22%at a duty cycle of 100%.This finding underscores the significance of incorporating pulse modulation in the microwave discharge process for ammonia synthesis.Furthermore,it was found that vibrational excitation of microwave plasma has a significant driving effect on ammonia synthesis.展开更多
基金supported by the Joint Research Fund in Astronomy(Grant Nos.U1931129,U1631115 and U1831117)under cooperative agreement between NSFC and Chinese Academy of Sciences(CAS)NSFC-STINT Grant 11611130023(CH2015-6360)the National Natural Science Foundation of China(NSFC,Grant No.11403054)
文摘This paper reports on the time and frequency standard system for the Five-hundred meter Aperture Spherical radio Telescope(FAST),including the system design,stability measurements and pulsar timing observations.The stability and drift rate of the frequency standard are calculated using 1-year monitoring data.The UTC-NIM Disciplined Oscillator(NIMDO)system improves the system time accuracy and stability to the level of 5 ns.Pulsar timing observations were carried out for several months.The weighted RMS of timing residuals reaches the level of less than 3.0μs.
基金the National Key R&D Program of China(No.2022YFB4101900)National Natural Science Foundation of China(Nos.22278305,U21B2096)Natural Science Foundation of Tianjin City(No.23JCZDJC00040)。
文摘A strategy for copper-catalyzed and biphosphine ligand controlled boracarboxylation of 1,3-dienes and CO_(2) with 3,4-selectivity was developed.The Cu Cl coupled with DPPF(1,1-bis(diphenylphosphino)ferrocene)was assigned to be the best catalyst,with 84%yield and exclusive3,4-selectivity.The ligand effect on both catalytic activity and regioselectivity of boracarboxylation was disclosed,which is rarely reported in any copper catalyzed boracarboxylation.The borocupration process is revealed to be a vital step for the biphosphine participated boracarboxylation of 1,3-dienes with CO_(2).The minimal substrate distortion occurring in 3,4-borocupration favors the 3,4-regioselectivity of boracarboxylation.The“pocket”confinement and suitableβ_(n)(92°–106°)of bisphosphine ligands are demonstrated to be in favour of the interaction between LCu-Bpin complex(the catalytic precursor)and1,3-diene substrate to decrease their interaction energyΔE_(int)(ζ)in 3,4-borocupration,thus promoting the 3,4-boracarboxylation.
基金This paper is the research result of the 2023 Undergraduate Teaching Reform Project of Higher Education in Guangxi,“Research on the Teaching Practice Model of Minority Music in Universities under the Background of Forging and Strengthening the Consciousness of the Chinese National Community”(2023JGA234).
文摘Against the strategic backdrop of forging and strengthening the consciousness of the Chinese national community in the new era,universities in border areas,as crucial platforms for the integration of multi-ethnic cultures,shoulder the significant mission of enhancing ethnic unity and promoting outstanding traditional Chinese culture.As an important carrier of Chinese culture,ethnic music not only contains profound historical memories and emotional identities but also demonstrates a powerful cultural and educational function in the teaching of border universities.Based on the actual situation of universities in border areas,this paper analyzes the unique value of ethnic music in cultivating students’national identity,cultural identity,and emotional identity,and explores effective paths for it to empower the forging and strengthening of the consciousness of the Chinese national community in teaching practice.By combining policy orientations and teaching status quo,the paper points out the main dilemmas such as single curriculum content,insufficient integration of ideological and political education,and a lack of practical resources,and proposes countermeasures such as strengthening the integration of ideological and political education,optimizing the curriculum structure,and expanding practical platforms.Through the deepening and innovation of ethnic music education,border universities can effectively enhance students’cultural consciousness and cultural confidence,providing solid educational support for forging and strengthening the consciousness of the Chinese national community.This paper has positive significance for promoting the high-quality development of education in border universities and constructing a new-era ethnic unity and progress education system.
基金supported by the National Natural Science Foundation of China(No.22201098)the Natural Science Foundation of Shandong Province(Nos.ZR2021QB005 and ZR2021MB008)Jinan City“New University 20”Project(No.202228113).
文摘Constructing a valid heterointerface with a built-in electric field is an effective strategy for designing energy storage anodes with exceptional efficiency for potassium-ion batteries(PIBs)and sodium-ion batteries(SIBs).In this study,WSe_(2)/MoSe_(2)nanosheets with a better-matched and stable heterojunction interface were uniformly embedded in carbon nanofiber frameworks(WSe_(2)/MoSe_(2)/CNFs).The ion/electron transfer kinetics were facilitated by heterointerfaces with an enlarged effective utilization range.Meanwhile,the heterointerface directed electron transfer from MoSe_(2)to WSe_(2)and had significant potassium adsorption capability.The ultra-high pseudocapacitance contribution originating from the heterostructure and morphological features of the WSe_(2)/MoSe_(2)nanosheets contributed to enhancing high-rate energy storage.Moreover,in situ X-ray diffraction and ex situ X-ray photoelectron spectroscopy revealed the potassification/depotassification behavior of the WSe_(2)/MoSe_(2)/CNFs during the conversion reaction.Consequently,after 500 cycles at 5 A·g^(-1),the WSe_(2)/MoSe_(2)/CNF anode demonstrated an outstanding long-term cycling performance of 125.6 mAh·g^(-1)for PIBs.While serving as a SIB electrode,it exhibited an exceptional rate capability of 243.5 mAh·g^(-1)at 20 A·g^(-1).With the goal of developing high-performance PIB/SIB electrode materials,the proposed strategy,based on heterointerface adaptation engineering,is promising.
基金supported by National Natural Science Foundation of China(Nos.52077026,51977023,52177126 and 12475253)the Fundamental Research Funds for the Central Universities(No.DUT23YG227)the Dalian Life&Health Guiding Project(No.2023ZXYG34)。
文摘In this study,we explored a one-step direct synthesis of NH3 under mild experimental conditions utilizing pulse-modulated microwave plasma technology at atmospheric pressure.At a substantial gas flow rate,a microwave plasma jet was formed and the microwave-assisted ammonia synthesis can be realized.Impacts of various parameters including the gas flow rate,gas component,microwave absorbed power,pulse modulation frequency,and pulse duty cycle on ammonia synthesis were systematically investigated.To indicate the reaction path of ammonia synthesis,the distributions of both the gas temperature and active species were also studied using optical emission spectra technology.It is found that a considerable amount of ammonia was directly synthesized without involvement of any catalysts,the highest ammonia production rate and energy efficiency(EE),up to 2.93μmol·min^(-1) and 6.64×10^(-2)g·(k W·h)^(-1),respectively,were achieved under low microwave power of 84.42 W.The duty cycle has obvious influences on the synthesis efficiency,compared to a duty cycle of 80%,the ammonia synthesis rate,EE and nitrogen conversion decreased by about 22%at a duty cycle of 100%.This finding underscores the significance of incorporating pulse modulation in the microwave discharge process for ammonia synthesis.Furthermore,it was found that vibrational excitation of microwave plasma has a significant driving effect on ammonia synthesis.
