The High Altitude Detection of Astronomical Radiation(HADAR)experiment,which was constructed in Tibet,China,combines the wide-angle advantages of traditional EAS array detectors with the high-sensitivity advantages of...The High Altitude Detection of Astronomical Radiation(HADAR)experiment,which was constructed in Tibet,China,combines the wide-angle advantages of traditional EAS array detectors with the high-sensitivity advantages of focused Cherenkov detectors.Its objective is to observe transient sources such as gamma-ray bursts and the counterparts of gravitational waves.This study aims to utilize the latest AI technology to enhance the sensitivity of HADAR experiments.Training datasets and models with distinctive creativity were constructed by incorporating the relevant physical theories for various applications.These models can determine the type,energy,and direction of the incident particles after careful design.We obtained a background identification accuracy of 98.6%,a relative energy reconstruction error of 10.0%,and an angular resolution of 0.22°in a test dataset at 10 TeV.These findings demonstrate the significant potential for enhancing the precision and dependability of detector data analysis in astrophysical research.By using deep learning techniques,the HADAR experiment’s observational sensitivity to the Crab Nebula has surpassed that of MAGIC and H.E.S.S.at energies below 0.5 TeV and remains competitive with conventional narrow-field Cherenkov telescopes at higher energies.In addition,our experiment offers a new approach for dealing with strongly connected,scattered data.展开更多
Thermoelectric properties of Al substituted compounds Ca3(Co1-xAlx)4O9 (x=0, 0.03, 0.05), prepared by a sol-gel process, have been investigated in the temperature range 305-20 K. The results indicate that after Al...Thermoelectric properties of Al substituted compounds Ca3(Co1-xAlx)4O9 (x=0, 0.03, 0.05), prepared by a sol-gel process, have been investigated in the temperature range 305-20 K. The results indicate that after Al substitution for Co in Ca3(Co1-xAlx)4O9, the direct current electrical resistivity and thermopower increase due to the reduction of carrier concentration. Experiments show that Al substitution results in decreased lattice thermal conductivity. The figure of merit of temperature behavior suggests that Ca3(Co0.97Al0.03)4O9 would be a promising candidate thermoelectric material for high-temperature thermoelectric application.展开更多
Metal organic framework(MOF) shows great potential in the research field of photocatalysis,and it is a big challenge to achieve efficient photocatalytic activity.In this work,we have successfully grown two-dimensional...Metal organic framework(MOF) shows great potential in the research field of photocatalysis,and it is a big challenge to achieve efficient photocatalytic activity.In this work,we have successfully grown two-dimensional MOF(2D-MOF) nanosheets on 2D-MOF nanosheets for the first time using a homometallic nodal strategy,and successfully prepared ultrathin nanosheets with tightly bound 2D/2D heterojunctions.2D Ni-BDC nanosheets were used as carriers to grow 2D Ni-TCPP nanosheets on top of them.Ni-TCPP has a high light absorption capacity,thus extending the light absorption range of 2D/2D heterojunctions.The tight coupling of the heterojunction effectively shortens the electron transfer distance,promotes the separation of interracial charges,and improves the photocatalytic activity.Particularly,Ni-BDC/Ni-TCPP-3can achieve to a hydrogen production rate of428.0 μmol·g^(-1),approximately 5.75 times higher than NiBDC and 5.24 times higher than Ni-TCPP,respectively.Thus,2D-MOF/2D-MOF heterojunctions provide a promising strategy for enhancing photocatalytic performance through rational heterostructure design with homometallic node strategy.展开更多
The observation of short gamma ray bursts(SGRBs)in the TeV energy range plays an important role in understanding the radiation mechanism and probing potential new physics,such as Lorentz invariance violation(LIV).Howe...The observation of short gamma ray bursts(SGRBs)in the TeV energy range plays an important role in understanding the radiation mechanism and probing potential new physics,such as Lorentz invariance violation(LIV).However,no SGRBs have been observed in this energy range owing to the short duration of SGRBs and the weakness of current experiments.New experiments with new technology are required to detect the very high energy(VHE)emission of SGRBs.In this study,we simulate the VHE γ-ray emissions from SGRBs and calculate the annu-al detection rate with the High Altitude Detection of Astronomical Radiation(HADAR)experiment.First,a set of pseudo-SGRB samples is generated and checked using the observations of the Fermi-GBM,Fermi-LAT,and Swift-BAT measurements.The annual detection rate is calculated from these SGRB samples based on the performance of the HADAR instrument.As a result,the HADAR experiment can detect 0.5 SGRBs per year if the spectral break-off of γ-rays caused by the internal absorption and Klein-Nishina(KN)effect is larger than 100 GeV.For a GRB090510-like GRB in HADAR's view,it should be possible to detect approximately 2000 photons considering the internal absorption and KN effect.With a time delay assumption due to LIV effects,a simulated light curve of GRB090510 has evident energy dependence.We hope that the HADAR experiment can perform SGRB observa-tions and test our calculations in the future.展开更多
The cosmic-ray total electron spectrum (electrons plus positrons) has been measured precisely up to TeV energies, with more interesting features found. Exhaustive analyses of the electron spectrum strongly support a...The cosmic-ray total electron spectrum (electrons plus positrons) has been measured precisely up to TeV energies, with more interesting features found. Exhaustive analyses of the electron spectrum strongly support a spectral hardening above 100 GeV, rather than a featureless single power-law, which is confirmed by the most recent observations. Meanwhile, the measurements of the DAMPE satellite have verified the presence of a knee-like structure around 1 TeV in the electron spectrum, resembling the cosmic-ray knee. In this paper, we establish a physical model in which the observed electron spectrum is composed of a superposition of CR sources with various spectral indices and high-energy cutoffs. The dispersion of the power index is assumed to be Gaussian, while the cutoff energy Ec follows a power-law distribution. These simple ideas can account naturally for both the hundred-GeV excess and the TeV spectral break.展开更多
文摘The High Altitude Detection of Astronomical Radiation(HADAR)experiment,which was constructed in Tibet,China,combines the wide-angle advantages of traditional EAS array detectors with the high-sensitivity advantages of focused Cherenkov detectors.Its objective is to observe transient sources such as gamma-ray bursts and the counterparts of gravitational waves.This study aims to utilize the latest AI technology to enhance the sensitivity of HADAR experiments.Training datasets and models with distinctive creativity were constructed by incorporating the relevant physical theories for various applications.These models can determine the type,energy,and direction of the incident particles after careful design.We obtained a background identification accuracy of 98.6%,a relative energy reconstruction error of 10.0%,and an angular resolution of 0.22°in a test dataset at 10 TeV.These findings demonstrate the significant potential for enhancing the precision and dependability of detector data analysis in astrophysical research.By using deep learning techniques,the HADAR experiment’s observational sensitivity to the Crab Nebula has surpassed that of MAGIC and H.E.S.S.at energies below 0.5 TeV and remains competitive with conventional narrow-field Cherenkov telescopes at higher energies.In addition,our experiment offers a new approach for dealing with strongly connected,scattered data.
基金financially supported by the Key Lab of Novel Thin Film Solar Cells,Chinese Academy of Sciences (No.KF201101)the Provincial Science Key Foundation of Higher Education Institutions of Anhui,China(No. KJ2011A053)the National Natural Science Foundation of China(No.51202005)
文摘Thermoelectric properties of Al substituted compounds Ca3(Co1-xAlx)4O9 (x=0, 0.03, 0.05), prepared by a sol-gel process, have been investigated in the temperature range 305-20 K. The results indicate that after Al substitution for Co in Ca3(Co1-xAlx)4O9, the direct current electrical resistivity and thermopower increase due to the reduction of carrier concentration. Experiments show that Al substitution results in decreased lattice thermal conductivity. The figure of merit of temperature behavior suggests that Ca3(Co0.97Al0.03)4O9 would be a promising candidate thermoelectric material for high-temperature thermoelectric application.
基金financially supported by the National Natural Science Foundation of China (Nos.62104003,21972065 and 21803002)the Natural Science Foundation of Anhui Province (No.1908085QB75)+3 种基金Anhui Provincial Natural Science Foundation for Distinguished Young Scholars (No.2008085J11)the Natural Science Foundation of Jiangsu Province (No.BK20220006)the Key projects of Anhui Provincial Department of Education,China (Nos.KJ2021ZD0044 and KJ2020A0228)Hefei National Laboratory for Physical Sciences at the Microscale (No.KF2020006)。
文摘Metal organic framework(MOF) shows great potential in the research field of photocatalysis,and it is a big challenge to achieve efficient photocatalytic activity.In this work,we have successfully grown two-dimensional MOF(2D-MOF) nanosheets on 2D-MOF nanosheets for the first time using a homometallic nodal strategy,and successfully prepared ultrathin nanosheets with tightly bound 2D/2D heterojunctions.2D Ni-BDC nanosheets were used as carriers to grow 2D Ni-TCPP nanosheets on top of them.Ni-TCPP has a high light absorption capacity,thus extending the light absorption range of 2D/2D heterojunctions.The tight coupling of the heterojunction effectively shortens the electron transfer distance,promotes the separation of interracial charges,and improves the photocatalytic activity.Particularly,Ni-BDC/Ni-TCPP-3can achieve to a hydrogen production rate of428.0 μmol·g^(-1),approximately 5.75 times higher than NiBDC and 5.24 times higher than Ni-TCPP,respectively.Thus,2D-MOF/2D-MOF heterojunctions provide a promising strategy for enhancing photocatalytic performance through rational heterostructure design with homometallic node strategy.
基金Supported by the National Natural Science Foundation of China(12263004,12263005,12275279)。
文摘The observation of short gamma ray bursts(SGRBs)in the TeV energy range plays an important role in understanding the radiation mechanism and probing potential new physics,such as Lorentz invariance violation(LIV).However,no SGRBs have been observed in this energy range owing to the short duration of SGRBs and the weakness of current experiments.New experiments with new technology are required to detect the very high energy(VHE)emission of SGRBs.In this study,we simulate the VHE γ-ray emissions from SGRBs and calculate the annu-al detection rate with the High Altitude Detection of Astronomical Radiation(HADAR)experiment.First,a set of pseudo-SGRB samples is generated and checked using the observations of the Fermi-GBM,Fermi-LAT,and Swift-BAT measurements.The annual detection rate is calculated from these SGRB samples based on the performance of the HADAR instrument.As a result,the HADAR experiment can detect 0.5 SGRBs per year if the spectral break-off of γ-rays caused by the internal absorption and Klein-Nishina(KN)effect is larger than 100 GeV.For a GRB090510-like GRB in HADAR's view,it should be possible to detect approximately 2000 photons considering the internal absorption and KN effect.With a time delay assumption due to LIV effects,a simulated light curve of GRB090510 has evident energy dependence.We hope that the HADAR experiment can perform SGRB observa-tions and test our calculations in the future.
基金Supported by National Natural Sciences Foundation of China(11663006,11747316,11135010,11405182)the Research Project of Chinese Ministry of Education(213036A)
文摘The cosmic-ray total electron spectrum (electrons plus positrons) has been measured precisely up to TeV energies, with more interesting features found. Exhaustive analyses of the electron spectrum strongly support a spectral hardening above 100 GeV, rather than a featureless single power-law, which is confirmed by the most recent observations. Meanwhile, the measurements of the DAMPE satellite have verified the presence of a knee-like structure around 1 TeV in the electron spectrum, resembling the cosmic-ray knee. In this paper, we establish a physical model in which the observed electron spectrum is composed of a superposition of CR sources with various spectral indices and high-energy cutoffs. The dispersion of the power index is assumed to be Gaussian, while the cutoff energy Ec follows a power-law distribution. These simple ideas can account naturally for both the hundred-GeV excess and the TeV spectral break.