The phosphors of ABF_4:Eu^(2+)and A_2SiF_6:Eu^(2+)(A=Na,K,Rb,Cs)have been synthesized,and the crystallographic data obtained accord with ASTM.In these materials,the f→f sharp lines emissions of Eu^(2+) were observed....The phosphors of ABF_4:Eu^(2+)and A_2SiF_6:Eu^(2+)(A=Na,K,Rb,Cs)have been synthesized,and the crystallographic data obtained accord with ASTM.In these materials,the f→f sharp lines emissions of Eu^(2+) were observed.The coordination numbers of Eu^(2+)in both NaBF_4 and Na_2SiF_6 hosts are less than 8.展开更多
Solar radio emission is among the most important tools for studying the solar corona;it allows us to determine the characteristics of the magnetic field,plasma,and energetic particles[1].The radio bursts with fine tem...Solar radio emission is among the most important tools for studying the solar corona;it allows us to determine the characteristics of the magnetic field,plasma,and energetic particles[1].The radio bursts with fine temporal and/or spectral structure in the dynamic spectra,i.e.,with short duration and/or narrow frequency band,are of special interest because they reflect fast processes at short spatial scales.展开更多
A novel fine spectral structure in solar radio bursts has been discovered using the Chashan broadband solar radio spectrometer at meter wavelengths(CBSm),an instrument of the Chinese Meridian Project-PhaseⅡ(CMP-Ⅱ).T...A novel fine spectral structure in solar radio bursts has been discovered using the Chashan broadband solar radio spectrometer at meter wavelengths(CBSm),an instrument of the Chinese Meridian Project-PhaseⅡ(CMP-Ⅱ).The structure features periodic narrow-band stripes with a typical recurrence time<1 s(occasionally reaching 8 s),often drifting from high to low frequencies and accompanied by absorptions,with trailing stripes appearing at the end of preceding ones.Some stripes exhibit periodic beaded(or pearl-like)enhancements with a periodicity of~0.1 s.The beaded stripes are reported for the first time ever.Data from the DAocheng Radio Telescope(DART)indicate a radio emission brightness temperature exceeding 10^(9)K,originating above brightening loops in active region AR 13664.We proposed a novel generation mechanism of the periodic stripes on the basis of the double plasma resonance(DPR)instability,and explained the beaded substructure in terms of modulation by low-frequency magnetohydrodynamic(MHD)waves.The study highlights the CBSm's capability to detect high-resolution fine spectral structures and offers novel insights into the emission mechanism and source characteristics of solar radio bursts.展开更多
Study is undertaken of spherical function spectral structures of long-term mean and anomaly patterns of the Northern Hemisphere 500 hPa monthly mean geopotential height together with the seasonal and interannual varia...Study is undertaken of spherical function spectral structures of long-term mean and anomaly patterns of the Northern Hemisphere 500 hPa monthly mean geopotential height together with the seasonal and interannual variations investigated.Results show that they are marked by low dimensions and low orders,and the mean and anomaly fields can be described in terms of 20 and 50 spherical function components,respectively.展开更多
In this paper, based on a discrete spectral problem and the corresponding zero curvature representation,the isospectral and nonisospectral lattice hierarchies are proposed. An algebraic structure of discrete zero curv...In this paper, based on a discrete spectral problem and the corresponding zero curvature representation,the isospectral and nonisospectral lattice hierarchies are proposed. An algebraic structure of discrete zero curvature equations is then established for such integrable systems. the commutation relations of Lax operators corresponding to the isospectral and non-isospectral lattice flows are worked out, the master symmetries of each lattice equation in the isospectral hierarchyand are generated, thus a τ-symmetry algebra for the lattice integrable systems is engendered from this theory.展开更多
We propose a nonparallel double-grating structure in a spectral-beam combining technique, where two gratings are placed nonparallel satisfying the Littrow mount in the focal region of the convergent lens. The most att...We propose a nonparallel double-grating structure in a spectral-beam combining technique, where two gratings are placed nonparallel satisfying the Littrow mount in the focal region of the convergent lens. The most attractive advantage of this approach is that it will compress the spectral span into half of its original spectrum, which means the number of combined elements can be doubled in the gain range of diode lasers. Experimental results demonstrate that the CW output power of the combined beam is 30.9 W with a spectral span of 7.0 nm, compared with its original spectrum span of 13.6 nm, and the spectral beam combining efficiency is 70.5%. In consideration that a single grating could have a high efficiency of 〉97% in a bandwidth of over ten nanometers, the efficiency loss of the grating pair should be less than 6%, which is acceptable for most applications, so this method of using double gratings should be highly interesting for practical applications when a nearly doubled number of diode lasers could be combined into one single laser compared with the previous single-grating methods.展开更多
We demonstrate spectral-furcated vector solitons in normal-dispersion fiber lasers comprising a section of polarizationmaintaining fiber.The spectrum of each orthogonal-polarized component is confined by the birefring...We demonstrate spectral-furcated vector solitons in normal-dispersion fiber lasers comprising a section of polarizationmaintaining fiber.The spectrum of each orthogonal-polarized component is confined by the birefringence-related phasematching principle,and the bicorn spectral structure corresponds to the zero-order sidebands of two vector modes.Due to the Hopf bifurcation effect,the vector soliton evolves into a breathing state at the higher pump level,accompanied by an extra set of sub-sidebands that continuously exchange energy with the zero-order sidebands.Simulation results fully reproduce experimental observations of the spectral furcation and soliton breathing,offering comprehensive insights into the pulse-shaping mechanism of the birefringence-managed soliton.展开更多
基金Project supported by the National Natural Science Foundation of China.
文摘The phosphors of ABF_4:Eu^(2+)and A_2SiF_6:Eu^(2+)(A=Na,K,Rb,Cs)have been synthesized,and the crystallographic data obtained accord with ASTM.In these materials,the f→f sharp lines emissions of Eu^(2+) were observed.The coordination numbers of Eu^(2+)in both NaBF_4 and Na_2SiF_6 hosts are less than 8.
文摘Solar radio emission is among the most important tools for studying the solar corona;it allows us to determine the characteristics of the magnetic field,plasma,and energetic particles[1].The radio bursts with fine temporal and/or spectral structure in the dynamic spectra,i.e.,with short duration and/or narrow frequency band,are of special interest because they reflect fast processes at short spatial scales.
基金supported by the National Natural Science Foundation of China(NNSFC)(Grant Nos.12103029,12303061,and 12203031)the Natural Science Foundation of Shandong Province(NSFSP)(Grant Nos.ZR2023QA074,and ZR2021QA033)the National Key R&D Program of China(Grant Nos.2022YFF0503002,and 2022YFF0503000)。
文摘A novel fine spectral structure in solar radio bursts has been discovered using the Chashan broadband solar radio spectrometer at meter wavelengths(CBSm),an instrument of the Chinese Meridian Project-PhaseⅡ(CMP-Ⅱ).The structure features periodic narrow-band stripes with a typical recurrence time<1 s(occasionally reaching 8 s),often drifting from high to low frequencies and accompanied by absorptions,with trailing stripes appearing at the end of preceding ones.Some stripes exhibit periodic beaded(or pearl-like)enhancements with a periodicity of~0.1 s.The beaded stripes are reported for the first time ever.Data from the DAocheng Radio Telescope(DART)indicate a radio emission brightness temperature exceeding 10^(9)K,originating above brightening loops in active region AR 13664.We proposed a novel generation mechanism of the periodic stripes on the basis of the double plasma resonance(DPR)instability,and explained the beaded substructure in terms of modulation by low-frequency magnetohydrodynamic(MHD)waves.The study highlights the CBSm's capability to detect high-resolution fine spectral structures and offers novel insights into the emission mechanism and source characteristics of solar radio bursts.
基金This work is sponsored by the Program on Long-Range Weather Forecasting Theory and Methodology of China.
文摘Study is undertaken of spherical function spectral structures of long-term mean and anomaly patterns of the Northern Hemisphere 500 hPa monthly mean geopotential height together with the seasonal and interannual variations investigated.Results show that they are marked by low dimensions and low orders,and the mean and anomaly fields can be described in terms of 20 and 50 spherical function components,respectively.
基金Supported by the National Science Foundation of China under Grant No.11371244the Applied Mathematical Subject of SSPU under Grant No.XXKPY1604
文摘In this paper, based on a discrete spectral problem and the corresponding zero curvature representation,the isospectral and nonisospectral lattice hierarchies are proposed. An algebraic structure of discrete zero curvature equations is then established for such integrable systems. the commutation relations of Lax operators corresponding to the isospectral and non-isospectral lattice flows are worked out, the master symmetries of each lattice equation in the isospectral hierarchyand are generated, thus a τ-symmetry algebra for the lattice integrable systems is engendered from this theory.
基金supported by the Shanghai Science and Technology Committee(Nos.16DZ2290102 and15JC1403500)the Chinese Academy of Sciences(No.QYZDJ-SSW-JSC014)the National Natural Science Foundation of China(No.61405216)
文摘We propose a nonparallel double-grating structure in a spectral-beam combining technique, where two gratings are placed nonparallel satisfying the Littrow mount in the focal region of the convergent lens. The most attractive advantage of this approach is that it will compress the spectral span into half of its original spectrum, which means the number of combined elements can be doubled in the gain range of diode lasers. Experimental results demonstrate that the CW output power of the combined beam is 30.9 W with a spectral span of 7.0 nm, compared with its original spectrum span of 13.6 nm, and the spectral beam combining efficiency is 70.5%. In consideration that a single grating could have a high efficiency of 〉97% in a bandwidth of over ten nanometers, the efficiency loss of the grating pair should be less than 6%, which is acceptable for most applications, so this method of using double gratings should be highly interesting for practical applications when a nearly doubled number of diode lasers could be combined into one single laser compared with the previous single-grating methods.
基金supported by the National Natural Science Foundation of China(No.12274344)the Natural Science Basic Research Program of Shaanxi Province(No.2021JC-09)the Fundamental Research Funds for the Central Universities(No.3102019JC008)。
文摘We demonstrate spectral-furcated vector solitons in normal-dispersion fiber lasers comprising a section of polarizationmaintaining fiber.The spectrum of each orthogonal-polarized component is confined by the birefringence-related phasematching principle,and the bicorn spectral structure corresponds to the zero-order sidebands of two vector modes.Due to the Hopf bifurcation effect,the vector soliton evolves into a breathing state at the higher pump level,accompanied by an extra set of sub-sidebands that continuously exchange energy with the zero-order sidebands.Simulation results fully reproduce experimental observations of the spectral furcation and soliton breathing,offering comprehensive insights into the pulse-shaping mechanism of the birefringence-managed soliton.
