Plasma radiation characteristics in EAST argon(Ar) gas and neon(Ne) gas seeding experiments are studied.The radiation profiles reconstructed from the fast bolometer measurement data by tomography method are compared w...Plasma radiation characteristics in EAST argon(Ar) gas and neon(Ne) gas seeding experiments are studied.The radiation profiles reconstructed from the fast bolometer measurement data by tomography method are compared with the ones got from the simulation program based on corona model.And the simulation results coincide roughly with the experimental data.For Ar seeding discharges,the substantial enhanced radiations can be generally observed in the edge areas at normalized radius ρ_(pol)~0.7–0.9,while the enhanced regions are more outer for Ne seeding discharges.The influence of seeded Ar gas on the core radiation is related to the injected position.In discharges with LSN divertor configuration,the Ar ions can permeate into the core region more easily when being injected from the opposite upper divertor ports.In USN divertor configuration,the W impurity sputtered from the upper divertor target plates are observed to be an important contributor to the increase of the core radiation no matter impurity seeding from any ports.The maximum radiated power fractions f_(rad)(P_(rad)/P_(heat)) about 60%–70% have been achieved in the recent EAST experimental campaign in 2015–2016.展开更多
In 2015 campaign,deuterium atomic emission spectra(D_(α))under the Zeeman effect in boundary region had been measured by a high resolution optical spectroscopic multichannel analysis(OSMA)system based on passive spec...In 2015 campaign,deuterium atomic emission spectra(D_(α))under the Zeeman effect in boundary region had been measured by a high resolution optical spectroscopic multichannel analysis(OSMA)system based on passive spectroscopy during the deuterium plasma discharge on EAST tokamak,and part of the works about the Zeeman effect on D_(α)spectra had already been done.However,the asymmetric phenomena of D_(α)emission spectra under the Zeeman effect were observed in process of analyzing the spectral data.To understand the asymmetric phenomena and acquire the useful local plasma information,an algorithm was proposed and used to analyze the asymmetry of the emission spectra under the Zeeman effect with all polarization components(πand±σ).In the algorithm,the neutral atoms were considered to follow the Maxwell distribution on EAST,and I+σ=I-σwas considered and set.Because of the line-averaged spectra along the viewing chord,the emission spectra were considered from two different regions:low-field side(LFS)and high-field side(HFS).Each spectral line was classified into three energy categories(the cold,warm,and hot)based on different atomic production processes in boundary recycling.The viewing angleθ(between the magnetic field B and the viewing chord),magnetic field B at two spectral emission positions(HFS and LFS)and the Doppler shift of all three energy categories of each spectral line were all considered in the algorithm.The effect of instrument function was also included here.The information of the boundary plasma were acquired,the reason for the asymmetric phenomena was discussed,and the boundary recycling during the discharge were studied in the paper.Based on fitting a statistical data of acquired fitting results,an important conclusion was acquired that the ratio of the spectral line intensity in HFS and LFS was proportional to the square of that of the corresponding magnetic field.展开更多
Atomically thin Pt nanolayers were synthesized on the surface of Mo2TiC2 MXenes and used for the catalytic dehydrogenation of ethane and propane into ethylene and propylene,two important chemicals for the petrochemica...Atomically thin Pt nanolayers were synthesized on the surface of Mo2TiC2 MXenes and used for the catalytic dehydrogenation of ethane and propane into ethylene and propylene,two important chemicals for the petrochemical industry.As compared with Pt nanoparticles,the atomically thin Pt nanolayer catalyst showed superior coke-resistance(no deactivation for 24 h),high activity(turnover frequencies(TOFs)of 0.4–1.2 s^(-1)),and selectivity(>95%)toward ethylene and propylene.The unique Pt nanolayer has a similar geometric surface to Pt nanoparticles,enabling the investigations of the electronic effect on the catalytic performance,where the geometric effect is negligible.It is found that the electronic effect plays a critical role in dehydrogenative product selectivity and catalyst stability.The metal–support interaction is found dependent on the substrate and metal components,providing wide opportunities to explore high-performance MXene-supported metallic catalysts.展开更多
For anode-free lithium metal battery,lithiophilic surface modification on the current collector can effectively reduce the lithium nucleation barrier,so as to regulate the electrodeposition of lithium.Here,atomically ...For anode-free lithium metal battery,lithiophilic surface modification on the current collector can effectively reduce the lithium nucleation barrier,so as to regulate the electrodeposition of lithium.Here,atomically dispersed Zn-(C/N/O)lithiophilic sites in the amorphous carbon medium were introduced onto Cu by an in-situ induced ion coordination chemistry strategy to get the modified Zn@NC@RGO@Cu current collector.X-ray absorption spectroscopy(XAS)combined with scanning transmission electron microscopy in high angle annular dark field(STEM-HAADF)analysis proved the single atomic state of the zinc sites surrounded by C,N,and O with a coordination number of~3.According to the electrochemical tests and first principle calculations,the ultra-uniformly dispersed Zn-(C/N/O)sites at the atomic level can effectively improve the lithium affinity,reduce the energy barrier for lithium nucleation,homogenize the lithium nucleation,and enhance an inorganic lithium compounds rich solid electrolyte interphase layer.As a result,the nucleation overpotential of lithium on the modified current collector was reduced to 7.7 mV,which was 5.4 times lower than that on bare Cu.Uniform lithium nucleation and deposition enabled stable Li plating/stripping and elevated Coulombic efficiency of 98.95%in Li||Cu cell after>850 cycles.Capacity retention of 89.7%was successfully achieved in the anode-free lithium metal battery after 100 cycles.展开更多
A MnOx–NbOx–CeO2 catalyst for low temperature selective catalytic reduction(SCR) of NOx with NH3 was prepared by a sol–gel method, and characterized by NH3–NO/NO2 SCR catalytic activity, NO/NH3 oxidation activity,...A MnOx–NbOx–CeO2 catalyst for low temperature selective catalytic reduction(SCR) of NOx with NH3 was prepared by a sol–gel method, and characterized by NH3–NO/NO2 SCR catalytic activity, NO/NH3 oxidation activity, NOx/NH3 TPD, XRD, BET, H2-TPR and in-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy(DRIFTS). The results indicate that the Mn Ox–Nb Ox–CeO2 catalyst shows excellent low temperature NH3-SCR activity in the temperature range of 150–300℃. Water vapor inhibits the low temperature activity of the catalyst in standard SCR due to the inhibition of NOx adsorption. As the NO2 content increases in the feed, water vapor does not affect the activity in NO2 SCR. Meanwhile, water vapor significantly enhances the N2 selectivity of the fresh and the aged catalysts due to its inhibition of the decomposition of NH4NO3 into N2O.展开更多
The Stokes-Einstein(SE) relation has been considered as one of the hallmarks of dynamics in liquids. It describes that the diffusion constant D is proportional to(τ/T)–1, where τ is the structural relaxation time a...The Stokes-Einstein(SE) relation has been considered as one of the hallmarks of dynamics in liquids. It describes that the diffusion constant D is proportional to(τ/T)–1, where τ is the structural relaxation time and T is the temperature. In many glassforming liquids, the breakdown of SE relation often occurred when the dynamics of the liquids becomes glassy, and its origin is still debated among many scientists. Using molecular dynamics simulations and support-vector machine method, it is found that the scaling between diffusion and relaxation fails when the total population of solid-like clusters shrinks at the maximal rate with decreasing temperature, which implies a dramatic unification of clusters into an extensive dominant one occurs at the time of breakdown of the SE relation. Our data leads to an interpretation that the SE violation in metallic glass-forming liquids can be attributed to a specific change in the atomic structures.展开更多
基金supported by National Natural Science Foundation of China (Grant Nos.11575247,11605243,11575244)National Magnetic Confinement Fusion Science Program of China (Grant No.2014GB124006)
文摘Plasma radiation characteristics in EAST argon(Ar) gas and neon(Ne) gas seeding experiments are studied.The radiation profiles reconstructed from the fast bolometer measurement data by tomography method are compared with the ones got from the simulation program based on corona model.And the simulation results coincide roughly with the experimental data.For Ar seeding discharges,the substantial enhanced radiations can be generally observed in the edge areas at normalized radius ρ_(pol)~0.7–0.9,while the enhanced regions are more outer for Ne seeding discharges.The influence of seeded Ar gas on the core radiation is related to the injected position.In discharges with LSN divertor configuration,the Ar ions can permeate into the core region more easily when being injected from the opposite upper divertor ports.In USN divertor configuration,the W impurity sputtered from the upper divertor target plates are observed to be an important contributor to the increase of the core radiation no matter impurity seeding from any ports.The maximum radiated power fractions f_(rad)(P_(rad)/P_(heat)) about 60%–70% have been achieved in the recent EAST experimental campaign in 2015–2016.
基金Project supported by the National Natural Science Foundation of China(Grant No.11805234)。
文摘In 2015 campaign,deuterium atomic emission spectra(D_(α))under the Zeeman effect in boundary region had been measured by a high resolution optical spectroscopic multichannel analysis(OSMA)system based on passive spectroscopy during the deuterium plasma discharge on EAST tokamak,and part of the works about the Zeeman effect on D_(α)spectra had already been done.However,the asymmetric phenomena of D_(α)emission spectra under the Zeeman effect were observed in process of analyzing the spectral data.To understand the asymmetric phenomena and acquire the useful local plasma information,an algorithm was proposed and used to analyze the asymmetry of the emission spectra under the Zeeman effect with all polarization components(πand±σ).In the algorithm,the neutral atoms were considered to follow the Maxwell distribution on EAST,and I+σ=I-σwas considered and set.Because of the line-averaged spectra along the viewing chord,the emission spectra were considered from two different regions:low-field side(LFS)and high-field side(HFS).Each spectral line was classified into three energy categories(the cold,warm,and hot)based on different atomic production processes in boundary recycling.The viewing angleθ(between the magnetic field B and the viewing chord),magnetic field B at two spectral emission positions(HFS and LFS)and the Doppler shift of all three energy categories of each spectral line were all considered in the algorithm.The effect of instrument function was also included here.The information of the boundary plasma were acquired,the reason for the asymmetric phenomena was discussed,and the boundary recycling during the discharge were studied in the paper.Based on fitting a statistical data of acquired fitting results,an important conclusion was acquired that the ratio of the spectral line intensity in HFS and LFS was proportional to the square of that of the corresponding magnetic field.
基金support from Iowa State University(Herbert L.Stiles Professorship).Y.X.and T.K.M.appreciate the start-up funding from the College of Engineering and Science at Louisiana Tech University.Z.W.W.and J.T.M.were supported by the National Science Foundation under Cooperative Agreement(NSF/ERC CISTAR,No.EEC-164772)Use of the Advanced Photon Source,a US Department of Energy Office of Basic Energy Sciences,was supported under contract no.DE-AC02-06CH11357.
文摘Atomically thin Pt nanolayers were synthesized on the surface of Mo2TiC2 MXenes and used for the catalytic dehydrogenation of ethane and propane into ethylene and propylene,two important chemicals for the petrochemical industry.As compared with Pt nanoparticles,the atomically thin Pt nanolayer catalyst showed superior coke-resistance(no deactivation for 24 h),high activity(turnover frequencies(TOFs)of 0.4–1.2 s^(-1)),and selectivity(>95%)toward ethylene and propylene.The unique Pt nanolayer has a similar geometric surface to Pt nanoparticles,enabling the investigations of the electronic effect on the catalytic performance,where the geometric effect is negligible.It is found that the electronic effect plays a critical role in dehydrogenative product selectivity and catalyst stability.The metal–support interaction is found dependent on the substrate and metal components,providing wide opportunities to explore high-performance MXene-supported metallic catalysts.
基金supported by Department of Science and Technology of Guangdong Province(No.211233812024)Guangdong Basic and Applied Basic Research Foundation(No.2021A1515110871)+1 种基金Shenzhen Science and Technology Program(Nos.JCYJ20220818101007016 and JCYJ20210324140804013)Tsinghua Shenzhen International Graduate School(No.QD2021005N).
文摘For anode-free lithium metal battery,lithiophilic surface modification on the current collector can effectively reduce the lithium nucleation barrier,so as to regulate the electrodeposition of lithium.Here,atomically dispersed Zn-(C/N/O)lithiophilic sites in the amorphous carbon medium were introduced onto Cu by an in-situ induced ion coordination chemistry strategy to get the modified Zn@NC@RGO@Cu current collector.X-ray absorption spectroscopy(XAS)combined with scanning transmission electron microscopy in high angle annular dark field(STEM-HAADF)analysis proved the single atomic state of the zinc sites surrounded by C,N,and O with a coordination number of~3.According to the electrochemical tests and first principle calculations,the ultra-uniformly dispersed Zn-(C/N/O)sites at the atomic level can effectively improve the lithium affinity,reduce the energy barrier for lithium nucleation,homogenize the lithium nucleation,and enhance an inorganic lithium compounds rich solid electrolyte interphase layer.As a result,the nucleation overpotential of lithium on the modified current collector was reduced to 7.7 mV,which was 5.4 times lower than that on bare Cu.Uniform lithium nucleation and deposition enabled stable Li plating/stripping and elevated Coulombic efficiency of 98.95%in Li||Cu cell after>850 cycles.Capacity retention of 89.7%was successfully achieved in the anode-free lithium metal battery after 100 cycles.
基金supported by the Ministry of Science and Technology of China (No. 2010CB732304)the Science and Technology Department of Zhejiang Province Project (No. 2011C31010)the National Natural Science Foundation of China (No. 51202126)
文摘A MnOx–NbOx–CeO2 catalyst for low temperature selective catalytic reduction(SCR) of NOx with NH3 was prepared by a sol–gel method, and characterized by NH3–NO/NO2 SCR catalytic activity, NO/NH3 oxidation activity, NOx/NH3 TPD, XRD, BET, H2-TPR and in-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy(DRIFTS). The results indicate that the Mn Ox–Nb Ox–CeO2 catalyst shows excellent low temperature NH3-SCR activity in the temperature range of 150–300℃. Water vapor inhibits the low temperature activity of the catalyst in standard SCR due to the inhibition of NOx adsorption. As the NO2 content increases in the feed, water vapor does not affect the activity in NO2 SCR. Meanwhile, water vapor significantly enhances the N2 selectivity of the fresh and the aged catalysts due to its inhibition of the decomposition of NH4NO3 into N2O.
基金the National Natural Science Foundation of China(Grant Nos.11804027,and 11525520)the National Basic Research Program of China(Grant No.2015CB856801)the Fundamental Research Funds for the Central Universities(Grant No.2018NTST24).
文摘The Stokes-Einstein(SE) relation has been considered as one of the hallmarks of dynamics in liquids. It describes that the diffusion constant D is proportional to(τ/T)–1, where τ is the structural relaxation time and T is the temperature. In many glassforming liquids, the breakdown of SE relation often occurred when the dynamics of the liquids becomes glassy, and its origin is still debated among many scientists. Using molecular dynamics simulations and support-vector machine method, it is found that the scaling between diffusion and relaxation fails when the total population of solid-like clusters shrinks at the maximal rate with decreasing temperature, which implies a dramatic unification of clusters into an extensive dominant one occurs at the time of breakdown of the SE relation. Our data leads to an interpretation that the SE violation in metallic glass-forming liquids can be attributed to a specific change in the atomic structures.
