Earth＇s variable rotation is mainly produced by the variability of the AAM（atmospheric angular momentum）. In particular, the axial AAM component X_3, which undergoes especially strong variations,induces changes in ...Earth＇s variable rotation is mainly produced by the variability of the AAM（atmospheric angular momentum）. In particular, the axial AAM component X_3, which undergoes especially strong variations,induces changes in the Earth＇s rotation rate. In this study we analysed maps of regional input into the effective axial AAM from 1948 through 2011 from NCEP/NCAR reanalysis. Global zonal circulation patterns related to the LOD（length of day） were described. We applied MSSA（Multichannel Singular Spectrum Analysis） jointly to the mass and motion components of AAM, which allowed us to extract annual, semiannual, 4-mo nth, quasi-biennial, 5-year, and low-frequency oscillations. PCs（Principal components） strongly related to ENSO（El Nino southern oscillation） were released. They can be used to study ENSO-induced changes in pressure and wind fields and their coupling to LOD. The PCs describing the trends have captured slow atmospheric circulation changes possibly related to climate variability.展开更多
The unknown γ-ray excess in the northwest region of Arp 220 was revisited by analyzing~11.8 years of the Fermi Large Area Telescope(Fermi-LAT) data in this study.We found that its photon flux was approximately three ...The unknown γ-ray excess in the northwest region of Arp 220 was revisited by analyzing~11.8 years of the Fermi Large Area Telescope(Fermi-LAT) data in this study.We found that its photon flux was approximately three times higher than that of the previous study in the 0.2-100 GeV band,and the corresponding significance level ~8.15σ was approximately four times higher than before.The light curves of 15 and 45 time bins from the whole time all showed two active periods,and the variability of the second period was more significant than that of the first period.The spectral indices from the two active periods were not statistically different and were close to the range of γ-ray flat-spectrum radio quasars observed by Fermi-LAT.Because the position of CRATES J153246+234400 was consistent with the best-fit position of our analysis,we suggest that CRATES J153246+234400 is more likely a γ-ray counterpart for the variational region.For Arp 220,there was no significant variability in the γ-ray emission.展开更多
用传输矩阵理论,研究了双周期一维光子晶体结构模型(A N B N)M的光传输特性。结果发现:当光正入射通过光子晶体时,光子禁带内有两个区域出现多条窄带透射峰,其透射率均为100%,两区域的透射峰数目可单独由周期数M来控制,且与M-1数值对应...用传输矩阵理论,研究了双周期一维光子晶体结构模型(A N B N)M的光传输特性。结果发现:当光正入射通过光子晶体时,光子禁带内有两个区域出现多条窄带透射峰,其透射率均为100%,两区域的透射峰数目可单独由周期数M来控制,且与M-1数值对应,可实现双系多通道光滤波功能;随着周期N的增大双系出现互相靠拢的趋势,同时双系透射峰会越来越锋锐,即周期数N的增大起到提高光滤波品质的作用;随着介质折射率的增大,双系透射峰带宽均变宽,而且透射峰劈裂变为振荡峰。双周期结构光子晶体的光传输特性,对设计双系多通道滤波器具有指导意义。展开更多
基金supported by Russian Foundation for Basic Research grants No. 17-05-00989, No. 16-05-00753,NRU HSE and visiting grants positions at Paris observatory and Wuhan university for the first authorpartially supported by grants by NSF/IGFA Belmont Forum Project (Grant No. ICER-1342644)the Chinese Academy of Sciences/SAFEA International Partnership Program for Creative Research Teams(Grant No. KZZD-EW-TZ-05)
文摘Earth＇s variable rotation is mainly produced by the variability of the AAM（atmospheric angular momentum）. In particular, the axial AAM component X_3, which undergoes especially strong variations,induces changes in the Earth＇s rotation rate. In this study we analysed maps of regional input into the effective axial AAM from 1948 through 2011 from NCEP/NCAR reanalysis. Global zonal circulation patterns related to the LOD（length of day） were described. We applied MSSA（Multichannel Singular Spectrum Analysis） jointly to the mass and motion components of AAM, which allowed us to extract annual, semiannual, 4-mo nth, quasi-biennial, 5-year, and low-frequency oscillations. PCs（Principal components） strongly related to ENSO（El Nino southern oscillation） were released. They can be used to study ENSO-induced changes in pressure and wind fields and their coupling to LOD. The PCs describing the trends have captured slow atmospheric circulation changes possibly related to climate variability.
基金the support for this work from the National Key R&D Program of China under Grant No.2018YFA0404204the National Natural Science Foundation of China(NSFC U1931113 and U1738211)+1 种基金the Foundations of Yunnan Province(2018IC059 and 2018FY001(-003))the scientific research fund of Yunnan Education Department(2020Y0039)。
文摘The unknown γ-ray excess in the northwest region of Arp 220 was revisited by analyzing~11.8 years of the Fermi Large Area Telescope(Fermi-LAT) data in this study.We found that its photon flux was approximately three times higher than that of the previous study in the 0.2-100 GeV band,and the corresponding significance level ~8.15σ was approximately four times higher than before.The light curves of 15 and 45 time bins from the whole time all showed two active periods,and the variability of the second period was more significant than that of the first period.The spectral indices from the two active periods were not statistically different and were close to the range of γ-ray flat-spectrum radio quasars observed by Fermi-LAT.Because the position of CRATES J153246+234400 was consistent with the best-fit position of our analysis,we suggest that CRATES J153246+234400 is more likely a γ-ray counterpart for the variational region.For Arp 220,there was no significant variability in the γ-ray emission.
文摘用传输矩阵理论,研究了双周期一维光子晶体结构模型(A N B N)M的光传输特性。结果发现:当光正入射通过光子晶体时,光子禁带内有两个区域出现多条窄带透射峰,其透射率均为100%,两区域的透射峰数目可单独由周期数M来控制,且与M-1数值对应,可实现双系多通道光滤波功能;随着周期N的增大双系出现互相靠拢的趋势,同时双系透射峰会越来越锋锐,即周期数N的增大起到提高光滤波品质的作用;随着介质折射率的增大,双系透射峰带宽均变宽,而且透射峰劈裂变为振荡峰。双周期结构光子晶体的光传输特性,对设计双系多通道滤波器具有指导意义。
