The chemical bond parameters and ionic polarizabilities in complex crystals are calculated.The mechanism of host influence on the nephelauxetic effect and hypersensitive transition is discussed.
Recent theoretical verification of self-similar and dissipative pure-quartic solitons(PQSs)emphasized the similarity between PQS lasers and conventional fiber lasers,but the unique equilibrium mechanism hinders the fo...Recent theoretical verification of self-similar and dissipative pure-quartic solitons(PQSs)emphasized the similarity between PQS lasers and conventional fiber lasers,but the unique equilibrium mechanism hinders the formation of PQS molecules in normal fourth-order dispersion(FOD)regimes.In this paper,we investigated the effect of filters on shaping PQSs in normal FOD based on a passively mode-locked fiber laser model.A bandpass filter eliminates the time pedestal of dissipative PQSs,thus realizing a multi-pulsing state.When the filter bandwidth is appropriate,the effective spectral filtering effect can lower the pulse splitting threshold and enable the coherent restoration from chaotic PQSs to PQS molecules.Additionally,changing the central wavelength of the filter can generate PQSs and PQS molecules with asymmetric intensity distributions.These results are important guides for the manipulation of PQSs and the construction of high repetition-frequency fiber lasers.展开更多
The spectral memory effect in scattering media is crucial for applications that employ broadband illumination,as it dictates the available spectral range from independent scattering responses.Previous studies mainly c...The spectral memory effect in scattering media is crucial for applications that employ broadband illumination,as it dictates the available spectral range from independent scattering responses.Previous studies mainly considered a passive result with the average impact of the scattering medium,whereas it is vital to actively enhance or suppress this effect for applications concerned with large spectral range or fine resolution.We construct an analytical model by integrating the concepts of wave-based interference and photon-based propagation,which manifests a potential physical image for active manipulation by utilizing scattering eigenchannels.Our theoretical predictions indicate that the spectral memory effect is enhanced using high-transmission eigenchannels while it is suppressed using low-transmission eigenchannels.These predictions are supported by finite-difference time-domain simulations and experiments,demonstrating that the spectral memory effect’s range can be actively manipulated.Quantitatively,the experiments achieved variations in enhancement and suppression that exceeded threefold(∼3.27).We clarify the underlying principles of the spectral memory effect in scattering media and demonstrate active manipulation of multispectral scattering processes.展开更多
The fifth generation (5G) wireless communication requires the massive multiple input multiple output (MIMO) technique. The massive MIMO antenna array of the millimeter wave (mm-wave) is recognized as a key enabler bec...The fifth generation (5G) wireless communication requires the massive multiple input multiple output (MIMO) technique. The massive MIMO antenna array of the millimeter wave (mm-wave) is recognized as a key enabler because of its high spectral efficiency. The higher the frequencies of the RF signal, the lower the distance it travels in free space caused by path loss, and it is more easily absorbed by obstacles, which are needed for high-gain transmitters. The advantage of the physical properties of higher New Radio (NR) frequencies is that 5G can utilize more spectrum, more antennas, and higher-order modulation schemes. The massive antennas and radio frequency chains improve the implementation of the cost of 5G wireless communication systems and result in an intense mutual coupling effect among antennas because of the limited space for deploying antennas. The upper bound of the effective capacity is derived for 5G multimedia massive MIMO communication systems. Two antennas that receive diversity gain models, the mutual coupling matrix, and the spacing antenna distance are built and analyzed. The impacts and affections of the antenna spacing the number of antennas, the quality-of-service (QoS) statistical exponent, and the number of independent incident directions on the upper effective capacity of 5G multimedia massive MIMO communication systems are analyzed. It is shown that for MIMO systems with compact transmit antenna arrays, the mutual coupling seriously degrades system capacity to mitigate the capacity degradation. In case of improvement in the mutual coupling by 99%, the system performance is kept stationary and enhances system capacity. However, the improvement of the mutual coupling is still about 87.5% today, which means the mutual coupling should be considered in 5G massive MIMO networks.展开更多
We demonstrate a fiber refractive index（RI） sensor based on an excessively tilted fiber grating（ExTFG）immobilized by large-size plasmonic gold nanoshells（GNSs）. The GNSs are covalently linked on ExTFG surface.Ex...We demonstrate a fiber refractive index（RI） sensor based on an excessively tilted fiber grating（ExTFG）immobilized by large-size plasmonic gold nanoshells（GNSs）. The GNSs are covalently linked on ExTFG surface.Experimental results demonstrate that both the intensity of the transverse magnetic（TM） and transverse electric（TE） modes of ExTFG are significantly modulated by the localized surface plasmon resonance（LSPR） of GNSs due to the wide-range absorption band. The wavelength RI sensitivities of the TM and TE modes in the low RI range of 1.333–1.379 are improved by ～25% and ～14% after GNSs immobilization, respectively, and the intensity RI sensitivities are ～599%/RIU and ～486%/RIU, respectively.展开更多
The underlying mechanism of the spectral cleaning effect of the cross-polarized wave（XPW） generation process was theoretically investigated. This study shows that the spectral noise of an input spectrum can be remov...The underlying mechanism of the spectral cleaning effect of the cross-polarized wave（XPW） generation process was theoretically investigated. This study shows that the spectral noise of an input spectrum can be removed in the XPW generation process and that the spectral cleaning effect depends on the characteristics of the input pulses, such as the chirp and Fourier-transform-limited duration of the initial pulse, and the modulation amplitude and frequency of the spectral noise. Though these factors codetermine the output spectrum of the XPW generation process, the spectral cleaning effect is mainly affected by the initial pulse chirp. The smoothing of the spectrum in the XPW generation process leads to a significant enhancement of the coherent contrast.展开更多
The influence of local site effects on seismic ground motions is an important issue in seismic hazard assessment and earthquake resistant design. Determining site effects in densely populated cities built on basins ca...The influence of local site effects on seismic ground motions is an important issue in seismic hazard assessment and earthquake resistant design. Determining site effects in densely populated cities built on basins can help to reduce the earthquake hazard. Site effects of Luoyang basin are estimated by the horizontal-to-vertical spectral ratio(HVSR) method using ambient noise records from a short-period dense array. The sites in Luoyang basin are sorted into three types according to the pattern of the HVSR curves. There are cases with a single clear peak, two clear peaks, and an unclear low frequency peak or multiple peaks, which correspond to there being one large impedance contrast interface, two large interfaces, and a moderate one beneath the sites, respectively. The site effects characterized by fundamental frequency from HVSR curves are affected by underlying sedimentary layers and depth of sedimentary basement. According to our results, the existence of thick sediment layer obviously lowers the fundamental frequency to the period range from 2 to 4 s in the downtown area of Luoyang city. The ground motion will amplify when through the sites and the buildings with height of 20–50 floors can resonate at the similar frequency domain. Site effects estimation using HVSR method from a short-period dense array is an effective technique in areas of moderate seismic risk where strong motion recordings are lacking, such as the Luoyang basin.展开更多
Atmospheric aerosols （acting as cloud condensation nuclei） can enhance the cloud droplet number concentration and reduce the cloud droplet size, and in turn affect the cloud optical depth, as well as the cloud albed...Atmospheric aerosols （acting as cloud condensation nuclei） can enhance the cloud droplet number concentration and reduce the cloud droplet size, and in turn affect the cloud optical depth, as well as the cloud albedo, and thereby exert a radiative influence on climate （the first indirect aerosol effect）. In this paper, based on various relationships between cloud droplet spectral dispersion （c） and cloud droplet number concentration （Nc）, we analytically derive the corresponding expressions of the cloud radiative forcing induced by changes in the cloud droplet number concentration. Further quantitative evaluation indicates that the cloud radiative forcing induced by aerosols for the different ^-Nc relationships varies from -29.1% to 25.2%, compared to the case without considering spectral dispersion （e = 0）. Our results suggest that an accurate description of e - Nc relationships helps to reduce the uncertainty of the first indirect aerosol effect and advances our scientific understanding of aerosol-cloud-radiation interactions.展开更多
The frequency band between 5 010 MHz and 5 030 MHz allocated as C band has been used as a candidate in the global navigation satellite systems （GNSS） along with more and more naviga- tion services in L band. The pot...The frequency band between 5 010 MHz and 5 030 MHz allocated as C band has been used as a candidate in the global navigation satellite systems （GNSS） along with more and more naviga- tion services in L band. The potential benefits and technical requirements of C band for satellite navi- gation have been analyzed before. However the degradation of effective carrier-power-to-noise densi- ty ratio（ A （C/No ）eu） based on code tracking spectral sensitivity coefficient（ CT_SSC ） as a compati- bility assessment methodology for potential GNSS radio frequency compatibility in C-Band has not been discussed clearly. So the compatibility of the signals in the C band between BeiDou （BD） B1 C and GPS L1C, L1C/A, Galileo E1Os as the interoperability or classical signals in L band is analyzed. Simulation results reveal the interference degree between BD III B1C and GPS L1C/A, L1C, Galileo E1OS. The results can also reveal that the multiplexed binary offset carrier （MBOC） and binary phase shift keying （BPSK） modulation is not appropriate for C band.展开更多
基金This Project is supported by the National Natural Science Foundation of Chinathe Laboratory of Rare Earth Physics and Chemistry,Changchun Institute of Applied Chemistry,Academia Sinica
文摘The chemical bond parameters and ionic polarizabilities in complex crystals are calculated.The mechanism of host influence on the nephelauxetic effect and hypersensitive transition is discussed.
基金Project supported by the National Natural Science Foundation of China(Grant No.62175116)。
文摘Recent theoretical verification of self-similar and dissipative pure-quartic solitons(PQSs)emphasized the similarity between PQS lasers and conventional fiber lasers,but the unique equilibrium mechanism hinders the formation of PQS molecules in normal fourth-order dispersion(FOD)regimes.In this paper,we investigated the effect of filters on shaping PQSs in normal FOD based on a passively mode-locked fiber laser model.A bandpass filter eliminates the time pedestal of dissipative PQSs,thus realizing a multi-pulsing state.When the filter bandwidth is appropriate,the effective spectral filtering effect can lower the pulse splitting threshold and enable the coherent restoration from chaotic PQSs to PQS molecules.Additionally,changing the central wavelength of the filter can generate PQSs and PQS molecules with asymmetric intensity distributions.These results are important guides for the manipulation of PQSs and the construction of high repetition-frequency fiber lasers.
基金supported by the National Natural Science Foundation of China(Grant Nos.12325408,92150102,62205302,92150301,12274129,12074121,62105101,62175066,12274139,and 12404380)the Fundamental and Applied Basic Research Project of Guangzhou(Grant No.2024A04J2001)the Guangdong Basic and Applied Basic Research Foundation(Grant Nos.2024B1515020051 and 2023A1515110742).
文摘The spectral memory effect in scattering media is crucial for applications that employ broadband illumination,as it dictates the available spectral range from independent scattering responses.Previous studies mainly considered a passive result with the average impact of the scattering medium,whereas it is vital to actively enhance or suppress this effect for applications concerned with large spectral range or fine resolution.We construct an analytical model by integrating the concepts of wave-based interference and photon-based propagation,which manifests a potential physical image for active manipulation by utilizing scattering eigenchannels.Our theoretical predictions indicate that the spectral memory effect is enhanced using high-transmission eigenchannels while it is suppressed using low-transmission eigenchannels.These predictions are supported by finite-difference time-domain simulations and experiments,demonstrating that the spectral memory effect’s range can be actively manipulated.Quantitatively,the experiments achieved variations in enhancement and suppression that exceeded threefold(∼3.27).We clarify the underlying principles of the spectral memory effect in scattering media and demonstrate active manipulation of multispectral scattering processes.
文摘The fifth generation (5G) wireless communication requires the massive multiple input multiple output (MIMO) technique. The massive MIMO antenna array of the millimeter wave (mm-wave) is recognized as a key enabler because of its high spectral efficiency. The higher the frequencies of the RF signal, the lower the distance it travels in free space caused by path loss, and it is more easily absorbed by obstacles, which are needed for high-gain transmitters. The advantage of the physical properties of higher New Radio (NR) frequencies is that 5G can utilize more spectrum, more antennas, and higher-order modulation schemes. The massive antennas and radio frequency chains improve the implementation of the cost of 5G wireless communication systems and result in an intense mutual coupling effect among antennas because of the limited space for deploying antennas. The upper bound of the effective capacity is derived for 5G multimedia massive MIMO communication systems. Two antennas that receive diversity gain models, the mutual coupling matrix, and the spacing antenna distance are built and analyzed. The impacts and affections of the antenna spacing the number of antennas, the quality-of-service (QoS) statistical exponent, and the number of independent incident directions on the upper effective capacity of 5G multimedia massive MIMO communication systems are analyzed. It is shown that for MIMO systems with compact transmit antenna arrays, the mutual coupling seriously degrades system capacity to mitigate the capacity degradation. In case of improvement in the mutual coupling by 99%, the system performance is kept stationary and enhances system capacity. However, the improvement of the mutual coupling is still about 87.5% today, which means the mutual coupling should be considered in 5G massive MIMO networks.
基金supported by the National Natural Science Foundation of China(Nos.61875026 and 61505017)the Foundation and Cutting-Edge Research Projects of the Chongqing Science and Technology Commission(No.cstc2018jcyjAX0122)the Graduate Student Innovation Program of the Chongqing University of Technology(No.ycx2018238)
文摘We demonstrate a fiber refractive index（RI） sensor based on an excessively tilted fiber grating（ExTFG）immobilized by large-size plasmonic gold nanoshells（GNSs）. The GNSs are covalently linked on ExTFG surface.Experimental results demonstrate that both the intensity of the transverse magnetic（TM） and transverse electric（TE） modes of ExTFG are significantly modulated by the localized surface plasmon resonance（LSPR） of GNSs due to the wide-range absorption band. The wavelength RI sensitivities of the TM and TE modes in the low RI range of 1.333–1.379 are improved by ～25% and ～14% after GNSs immobilization, respectively, and the intensity RI sensitivities are ～599%/RIU and ～486%/RIU, respectively.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11127901,61521093,and 61505234)the International S&T Cooperation of Program of China(Grant No.2016YFE0119300)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB160301)the Youth Innovation Promotion Association,Chinese Academy of Sciences
文摘The underlying mechanism of the spectral cleaning effect of the cross-polarized wave（XPW） generation process was theoretically investigated. This study shows that the spectral noise of an input spectrum can be removed in the XPW generation process and that the spectral cleaning effect depends on the characteristics of the input pulses, such as the chirp and Fourier-transform-limited duration of the initial pulse, and the modulation amplitude and frequency of the spectral noise. Though these factors codetermine the output spectrum of the XPW generation process, the spectral cleaning effect is mainly affected by the initial pulse chirp. The smoothing of the spectrum in the XPW generation process leads to a significant enhancement of the coherent contrast.
基金funded by the National Key R&D Program of China(No.2017YFC1500202)supported by the National Natural Science Foundation of China(No.41604048)China Earthquake Science Experiment(No.2016CESE0103)
文摘The influence of local site effects on seismic ground motions is an important issue in seismic hazard assessment and earthquake resistant design. Determining site effects in densely populated cities built on basins can help to reduce the earthquake hazard. Site effects of Luoyang basin are estimated by the horizontal-to-vertical spectral ratio(HVSR) method using ambient noise records from a short-period dense array. The sites in Luoyang basin are sorted into three types according to the pattern of the HVSR curves. There are cases with a single clear peak, two clear peaks, and an unclear low frequency peak or multiple peaks, which correspond to there being one large impedance contrast interface, two large interfaces, and a moderate one beneath the sites, respectively. The site effects characterized by fundamental frequency from HVSR curves are affected by underlying sedimentary layers and depth of sedimentary basement. According to our results, the existence of thick sediment layer obviously lowers the fundamental frequency to the period range from 2 to 4 s in the downtown area of Luoyang city. The ground motion will amplify when through the sites and the buildings with height of 20–50 floors can resonate at the similar frequency domain. Site effects estimation using HVSR method from a short-period dense array is an effective technique in areas of moderate seismic risk where strong motion recordings are lacking, such as the Luoyang basin.
基金jointly supported by the National Natural Science Foundation of China (Grant No. 41105071)the CAS Strategic Priority Research Program (Grant No. XDA05110101)the National Basic Research Program of China (Grant No. 2011CB403406)
文摘Atmospheric aerosols （acting as cloud condensation nuclei） can enhance the cloud droplet number concentration and reduce the cloud droplet size, and in turn affect the cloud optical depth, as well as the cloud albedo, and thereby exert a radiative influence on climate （the first indirect aerosol effect）. In this paper, based on various relationships between cloud droplet spectral dispersion （c） and cloud droplet number concentration （Nc）, we analytically derive the corresponding expressions of the cloud radiative forcing induced by changes in the cloud droplet number concentration. Further quantitative evaluation indicates that the cloud radiative forcing induced by aerosols for the different ^-Nc relationships varies from -29.1% to 25.2%, compared to the case without considering spectral dispersion （e = 0）. Our results suggest that an accurate description of e - Nc relationships helps to reduce the uncertainty of the first indirect aerosol effect and advances our scientific understanding of aerosol-cloud-radiation interactions.
基金Supported by the National High Technology Research and Development Program of China(863Program)(2011AA120502)
文摘The frequency band between 5 010 MHz and 5 030 MHz allocated as C band has been used as a candidate in the global navigation satellite systems （GNSS） along with more and more naviga- tion services in L band. The potential benefits and technical requirements of C band for satellite navi- gation have been analyzed before. However the degradation of effective carrier-power-to-noise densi- ty ratio（ A （C/No ）eu） based on code tracking spectral sensitivity coefficient（ CT_SSC ） as a compati- bility assessment methodology for potential GNSS radio frequency compatibility in C-Band has not been discussed clearly. So the compatibility of the signals in the C band between BeiDou （BD） B1 C and GPS L1C, L1C/A, Galileo E1Os as the interoperability or classical signals in L band is analyzed. Simulation results reveal the interference degree between BD III B1C and GPS L1C/A, L1C, Galileo E1OS. The results can also reveal that the multiplexed binary offset carrier （MBOC） and binary phase shift keying （BPSK） modulation is not appropriate for C band.
