Difficulty in extracting nonlinear sparse impulse features due to variable speed conditions and redundant noise interference leads to challenges in diagnosing variable speed faults.Therefore,an improved spectral amplit...Difficulty in extracting nonlinear sparse impulse features due to variable speed conditions and redundant noise interference leads to challenges in diagnosing variable speed faults.Therefore,an improved spectral amplitude modulation(ISAM)based on sparse feature adaptive convolution(SFAC)is proposed to enhance the fault features under variable speed conditions.First,an optimal bi-damped wavelet construction method is proposed to learn signal impulse features,which selects the optimal bi-damped wavelet parameters with correlation criterion and particle swarm optimization.Second,a convolutional basis pursuit denoising model based on an optimal bi-damped wavelet is proposed for resolving sparse impulses.A model regularization parameter selection method based on weighted fault characteristic amplitude ratio assistance is proposed.Then,an ISAM method based on kurtosis threshold is proposed to further enhance the fault information of sparse signal.Finally,the type of variable speed faults is determined by order spectrum analysis.Various experimental results,such as spectral amplitude modulation and Morlet wavelet matching,verify the effectiveness and advantages of the ISAM-SFAC method.展开更多
In this work,polarization mode dispersion(PMD)in polarization-maintaining(PM)fibers,to the best of our knowledge,is first proposed and experimentally proved to be responsible for severe spectral modulations in ultrafa...In this work,polarization mode dispersion(PMD)in polarization-maintaining(PM)fibers,to the best of our knowledge,is first proposed and experimentally proved to be responsible for severe spectral modulations in ultrafast PM fiber amplifiers,the introduction of which can give reasonable explanation for the dense spectral ripples imposed on the spectra of amplified lasers from the commonly used all-PM-fiber or hybrid“PM-fiber+bulk crystal”amplifiers,including both high-power amplifiers with remarkable nonlinear effects(self-phase modulation,SPM)and even low-power amplifiers with negligible nonlinear effects.展开更多
All-season thermal management with zero energy consumption and emissions is more crucial to global decarbonization over traditional energy-intensive cooling/heating systems.However,the static single thermal management...All-season thermal management with zero energy consumption and emissions is more crucial to global decarbonization over traditional energy-intensive cooling/heating systems.However,the static single thermal management for cooling or heating fails to self-regulate the temperature in dynamic seasonal temperature condition.Herein,inspired by the dual-temperature regulation function of the fur color changes on the backs and abdomens of penguins,a smart thermal management composite hydrogel(PNA@H-PM Gel)system was subtly created though an"on-demand"dual-layer structure design strategy.The PNA@H-PM Gel system features synchronous solar and thermal radiation modulation as well as tunable phase transition temperatures to meet the variable seasonal thermal requirements and energy-saving demands via self-adaptive radiative cooling and solar heating regulation.Furthermore,this system demonstrates superb modulations of both the solar reflectance(ΔR=0.74)and thermal emissivity(ΔE=0.52)in response to ambient temperature changes,highlighting efficient temperature regulation with average radiative cooling and solar heating effects of 9.6℃in summer and 6.1℃in winter,respectively.Moreover,compared to standard building baselines,the PNA@H-PM Gel presents a more substantial energy-saving cooling/heating potentials for energy-efficient buildings across various regions and climates.This novel solution,inspired by penguins in the real world,will offer a fresh approach for producing intelligent,energy-saving thermal management materials,and serve for temperature regulation under dynamic climate conditions and even throughout all seasons.展开更多
Aiming at the problem of music noise introduced by classical spectral subtraction,a shorttime modulation domain(STM)spectral subtraction method has been successfully applied for singlechannel speech enhancement.Howeve...Aiming at the problem of music noise introduced by classical spectral subtraction,a shorttime modulation domain(STM)spectral subtraction method has been successfully applied for singlechannel speech enhancement.However,due to the inaccurate voice activity detection(VAD),the residual music noise and enhanced performance still need to be further improved,especially in the low signal to noise ratio(SNR)scenarios.To address this issue,an improved frame iterative spectral subtraction in the STM domain(IMModSSub)is proposed.More specifically,with the inter-frame correlation,the noise subtraction is directly applied to handle the noisy signal for each frame in the STM domain.Then,the noisy signal is classified into speech or silence frames based on a predefined threshold of segmented SNR.With these classification results,a corresponding mask function is developed for noisy speech after noise subtraction.Finally,exploiting the increased sparsity of speech signal in the modulation domain,the orthogonal matching pursuit(OMP)technique is employed to the speech frames for improving the speech quality and intelligibility.The effectiveness of the proposed method is evaluated with three types of noise,including white noise,pink noise,and hfchannel noise.The obtained results show that the proposed method outperforms some established baselines at lower SNRs(-5 to +5 dB).展开更多
An optical modulation format generation scheme based on spectral filtering and frequency-to-time mapping is experimentally demonstrated. Many modulation formats with continuously adjustable duty radio and bit rate can...An optical modulation format generation scheme based on spectral filtering and frequency-to-time mapping is experimentally demonstrated. Many modulation formats with continuously adjustable duty radio and bit rate can be formed by changing the dispersion of dispersion element and the bandwidth of shaped spectrum in this scheme. In the experiment, non-return-to-zero(NRZ) signal with bit rate of 29.41 Gbit/s and 1/2 duty ratio return-to-zero(RZ) signal with bit rate of 13.51 Gbit/s are obtained. The maximum bit rate of modulation format signal is also analyzed.展开更多
Polarization-based detection technologies have broad applications across various fields.Integrating polarization with interferometric imaging holds significant promise for simultaneously capturing three-dimensional st...Polarization-based detection technologies have broad applications across various fields.Integrating polarization with interferometric imaging holds significant promise for simultaneously capturing three-dimensional structure and polarization information.However,existing interferometric polarization measurement methods often rely on complex setups and sacrifice the acquisition rate or axial imaging range for parameter diversity.展开更多
For absorption linewidth inversion with wavelength modulation spectroscopy（WMS）, an optimized WMS spectral line fitting method was demonstrated to infer absorption linewidth effectively, and the analytical expressio...For absorption linewidth inversion with wavelength modulation spectroscopy（WMS）, an optimized WMS spectral line fitting method was demonstrated to infer absorption linewidth effectively, and the analytical expressions for relationships between Lorentzian linewidth and the separations of first harmonic peak-to-valley and second harmonic zero-crossing were deduced. The transition of CO_2 centered at 4991.25 cm^（-1） was used to verify the optimized spectral fitting method and the analytical expressions. Results showed that the optimized spectra fitting method was able to infer absorption accurately and compute more than 10 times faster than the commonly used numerical fitting procedure. The second harmonic zero-crossing separation method calculated an even 6 orders faster than the spectra fitting without losing any accuracy for Lorentzian dominated cases. Additionally, linewidth calculated through second harmonic zero-crossing was preferred for much smaller error than the first harmonic peak-to-valley separation method. The presented analytical expressions can also be used in on-line optical sensing applications, electron paramagnetic resonance, and further theoretical characterization of absorption lineshape.展开更多
Cubic rock salt can lower down or break the rare earth transition barrier through interstitial or vacancy defects owing to its great deformation and rotationflexibility.Here,we demonstrate that oxygen vacancies in SrO ...Cubic rock salt can lower down or break the rare earth transition barrier through interstitial or vacancy defects owing to its great deformation and rotationflexibility.Here,we demonstrate that oxygen vacancies in SrO are induced by proper oxidization and atmosphere adjustment,resulting in defects with various depths and crystalfield distortion.The thermally assisted tunneling from defects to 5 D_(4) state and electronic population decrease on 5 D_(3) state of Tb^(3+)þare observed by the deformation of adjacent oxygen octahedral structure.Finally,the asprepared SrO:0.01 Tb^(3+)þphosphors,commercial BaMgAl10O17:Eu^(2+)þblue phosphor,and CaAlSiN3:Eu^(2+)þred phosphor are mixed and coated onto 280 nm deep-ultraviolet LED chip to assemble white light-emitting LED device.The LEDs show CCT of 3850 K,4136 K,and 4741 K,with color rendering index of 90.3,90.8,and 92.1,respectively.These insights will advance the fundamental knowledge of crystal engineering in cubic rock salt,and enable new ways to manipulate energy transfer and electronic transition via defects.展开更多
We theoretically and experimentally study the polarization and phase control of two-photon absorption in an isotropic molecular system. We theoretically show that the two-photon transition probability decreases when t...We theoretically and experimentally study the polarization and phase control of two-photon absorption in an isotropic molecular system. We theoretically show that the two-photon transition probability decreases when the laser polarization changes from linear through elliptical to circular, and the laser polarization does not affect the control efficiency of two-photon transition probability by shaping the spectral phase. These theoretical results are experimentally confirmed in coumarin 480. Furthermore, we propose that the combination of the laser polarization with the spectral phase modulation can further increase the control efficiency of the two-photon absorption.展开更多
Optical transmission technologies have gone through several generations of development.Spectral efficiency has significant ly improved,and industry has begun to search for an answer to a basic question：What are the f...Optical transmission technologies have gone through several generations of development.Spectral efficiency has significant ly improved,and industry has begun to search for an answer to a basic question：What are the fundamental linear and nonlin ear signal channel limitations of the Shannon theory when there is no compensation in an optical fiber transmission system？Next-generation technologies should exceed the 100G transmis sion capability of coherent systems in order to approach the Shannon limit.Spectral efficiency first needs to be improved be fore overall transmission capability can be improved.The means to improve spectral efficiency include more complex modulation formats and channel encoding/decoding algorithms,prefiltering with multisymbol detection,optical OFDM and Ny quist WDM multicarrier technologies,and nonlinearity compen sation.With further optimization,these technologies will most likely be incorporated into beyond-100G optical transport sys tems to meet bandwidth demand.展开更多
Multi-spectral and multi-functional optical components play a crucial role in fields such as high-speed communications and optical sensing.However,the interaction between different spectra and matter varies significan...Multi-spectral and multi-functional optical components play a crucial role in fields such as high-speed communications and optical sensing.However,the interaction between different spectra and matter varies significantly,making it challenging to simultaneously achieve dynamic multi-spectral modulation capabilities.We designed a modulator based on a planar nested multiscale metasurface,incorporating silicon(Si)and perovskite as control materials,to modulate both microwave and terahertz(THz)ranges.展开更多
Passive daytime radiative cooling(PDRC)technology has great potential in reducing cooling energy consumption.In order to further improve the spectral performance of PDRC coatings,current researchers mostly focus on th...Passive daytime radiative cooling(PDRC)technology has great potential in reducing cooling energy consumption.In order to further improve the spectral performance of PDRC coatings,current researchers mostly focus on the selection and size design of functional particles,while ignoring the optical properties enhancement effect caused by the interlayer binder.In this study,based on the principle that the refractive index difference between layers enhanced the backscattering performance of the solar spectrum,we proposed and manufactured a double-layer PDRC coating with polyvinylidene difluoride(PVDF)as the filmforming material in the upper layer and polydimethylsiloxane(PDMS)as the film-forming material in the lower layer,both filled with Al_(2)O_(3) and SiO_(2) particles.The double-layer PDRC coating exhibited excellent spectral performance that a high solar reflectivity of 98%and an emissivity of 0.95 at the“atmospheric window”band.In comparison,the solar spectrum reflectivity of the single-layer PDRC coatings based on PVDF and PDMS of the same thickness was 95%and 94.7%,respectively.Outdoor tests showed that the PDRC coating achieved a temperature decrease of up to 7.1℃ under direct sunlight at noon time.In addition,the PDRC coating had excellent weather resistance,water resistance,and other basic properties.This article opens up a new idea and provides methodological guidance for the design of double-layer PDRC coatings.展开更多
基金funded by the National Natural Science Foundation of China(grant nos.52475084 and 52375076)the Postdoctoral Fellowship Program of CPSF(grant no.GZC20230202).
文摘Difficulty in extracting nonlinear sparse impulse features due to variable speed conditions and redundant noise interference leads to challenges in diagnosing variable speed faults.Therefore,an improved spectral amplitude modulation(ISAM)based on sparse feature adaptive convolution(SFAC)is proposed to enhance the fault features under variable speed conditions.First,an optimal bi-damped wavelet construction method is proposed to learn signal impulse features,which selects the optimal bi-damped wavelet parameters with correlation criterion and particle swarm optimization.Second,a convolutional basis pursuit denoising model based on an optimal bi-damped wavelet is proposed for resolving sparse impulses.A model regularization parameter selection method based on weighted fault characteristic amplitude ratio assistance is proposed.Then,an ISAM method based on kurtosis threshold is proposed to further enhance the fault information of sparse signal.Finally,the type of variable speed faults is determined by order spectrum analysis.Various experimental results,such as spectral amplitude modulation and Morlet wavelet matching,verify the effectiveness and advantages of the ISAM-SFAC method.
基金supported by the National Natural Science Foundation of China(Nos.62375156,62075116,62075117)the Foundation of Qilu Young Scholar from Shandong University。
文摘In this work,polarization mode dispersion(PMD)in polarization-maintaining(PM)fibers,to the best of our knowledge,is first proposed and experimentally proved to be responsible for severe spectral modulations in ultrafast PM fiber amplifiers,the introduction of which can give reasonable explanation for the dense spectral ripples imposed on the spectra of amplified lasers from the commonly used all-PM-fiber or hybrid“PM-fiber+bulk crystal”amplifiers,including both high-power amplifiers with remarkable nonlinear effects(self-phase modulation,SPM)and even low-power amplifiers with negligible nonlinear effects.
基金the funding and generous support of the National Natural Science Foundation of China(52103263,52271249)the Key Project of International Science&Technology Cooperation of Shaanxi Province(2023-GHZD-09)+5 种基金the Key Project of Science Foundation of Education Department of Shaanxi Province(22JY011)the Key Project of Scientific Research and Development of Shaanxi Province(2023GXLH-070)the Qinchuangyuan"Scientist+Engineer"Team of Shaanxi Province(2023KXJ-069)the Key Research and Development Program of Shaanxi(2023-YBGY-488)the Sci-tech Innovation Team of Shaanxi Province(2024RS-CXTD-46)the Key Research and Development Program of Shaanxi Province(2020ZDLGY13-11).
文摘All-season thermal management with zero energy consumption and emissions is more crucial to global decarbonization over traditional energy-intensive cooling/heating systems.However,the static single thermal management for cooling or heating fails to self-regulate the temperature in dynamic seasonal temperature condition.Herein,inspired by the dual-temperature regulation function of the fur color changes on the backs and abdomens of penguins,a smart thermal management composite hydrogel(PNA@H-PM Gel)system was subtly created though an"on-demand"dual-layer structure design strategy.The PNA@H-PM Gel system features synchronous solar and thermal radiation modulation as well as tunable phase transition temperatures to meet the variable seasonal thermal requirements and energy-saving demands via self-adaptive radiative cooling and solar heating regulation.Furthermore,this system demonstrates superb modulations of both the solar reflectance(ΔR=0.74)and thermal emissivity(ΔE=0.52)in response to ambient temperature changes,highlighting efficient temperature regulation with average radiative cooling and solar heating effects of 9.6℃in summer and 6.1℃in winter,respectively.Moreover,compared to standard building baselines,the PNA@H-PM Gel presents a more substantial energy-saving cooling/heating potentials for energy-efficient buildings across various regions and climates.This novel solution,inspired by penguins in the real world,will offer a fresh approach for producing intelligent,energy-saving thermal management materials,and serve for temperature regulation under dynamic climate conditions and even throughout all seasons.
基金National Natural Science Foundation of China(NSFC)(No.61671075)Major Program of National Natural Science Foundation of China(No.61631003)。
文摘Aiming at the problem of music noise introduced by classical spectral subtraction,a shorttime modulation domain(STM)spectral subtraction method has been successfully applied for singlechannel speech enhancement.However,due to the inaccurate voice activity detection(VAD),the residual music noise and enhanced performance still need to be further improved,especially in the low signal to noise ratio(SNR)scenarios.To address this issue,an improved frame iterative spectral subtraction in the STM domain(IMModSSub)is proposed.More specifically,with the inter-frame correlation,the noise subtraction is directly applied to handle the noisy signal for each frame in the STM domain.Then,the noisy signal is classified into speech or silence frames based on a predefined threshold of segmented SNR.With these classification results,a corresponding mask function is developed for noisy speech after noise subtraction.Finally,exploiting the increased sparsity of speech signal in the modulation domain,the orthogonal matching pursuit(OMP)technique is employed to the speech frames for improving the speech quality and intelligibility.The effectiveness of the proposed method is evaluated with three types of noise,including white noise,pink noise,and hfchannel noise.The obtained results show that the proposed method outperforms some established baselines at lower SNRs(-5 to +5 dB).
基金supported by the National Natural Science Foundation of China(No.61377075)the Tianjin Natural Science Foundation(No.17JCYBJC16600)
文摘An optical modulation format generation scheme based on spectral filtering and frequency-to-time mapping is experimentally demonstrated. Many modulation formats with continuously adjustable duty radio and bit rate can be formed by changing the dispersion of dispersion element and the bandwidth of shaped spectrum in this scheme. In the experiment, non-return-to-zero(NRZ) signal with bit rate of 29.41 Gbit/s and 1/2 duty ratio return-to-zero(RZ) signal with bit rate of 13.51 Gbit/s are obtained. The maximum bit rate of modulation format signal is also analyzed.
基金National Natural Science Foundation of China(12404345,62375144)Tianjin Natural Science Foundation(22JCZDJC00160)+1 种基金Fundamental Research Funds for the Central Universities,Nankai University(63241331)China Postdoctoral Science Foundation(2023M731787)。
文摘Polarization-based detection technologies have broad applications across various fields.Integrating polarization with interferometric imaging holds significant promise for simultaneously capturing three-dimensional structure and polarization information.However,existing interferometric polarization measurement methods often rely on complex setups and sacrifice the acquisition rate or axial imaging range for parameter diversity.
基金Project supported by the National Natural Science Foundation of China(Grant No.61505142)the Tianjin Natural Science Foundation(Grant No.16JCQNJC02100)
文摘For absorption linewidth inversion with wavelength modulation spectroscopy（WMS）, an optimized WMS spectral line fitting method was demonstrated to infer absorption linewidth effectively, and the analytical expressions for relationships between Lorentzian linewidth and the separations of first harmonic peak-to-valley and second harmonic zero-crossing were deduced. The transition of CO_2 centered at 4991.25 cm^（-1） was used to verify the optimized spectral fitting method and the analytical expressions. Results showed that the optimized spectra fitting method was able to infer absorption accurately and compute more than 10 times faster than the commonly used numerical fitting procedure. The second harmonic zero-crossing separation method calculated an even 6 orders faster than the spectra fitting without losing any accuracy for Lorentzian dominated cases. Additionally, linewidth calculated through second harmonic zero-crossing was preferred for much smaller error than the first harmonic peak-to-valley separation method. The presented analytical expressions can also be used in on-line optical sensing applications, electron paramagnetic resonance, and further theoretical characterization of absorption lineshape.
基金supported by the Natural Science Foundation of Zhejiang Province(Grant No.LQ21E020006)the Fundamental Research Funds for the Provincial Universities of Zhejiang(Grant No.2021YW46)the National Natural Science Foundation of China(Grant 62205322,22090043).
文摘Cubic rock salt can lower down or break the rare earth transition barrier through interstitial or vacancy defects owing to its great deformation and rotationflexibility.Here,we demonstrate that oxygen vacancies in SrO are induced by proper oxidization and atmosphere adjustment,resulting in defects with various depths and crystalfield distortion.The thermally assisted tunneling from defects to 5 D_(4) state and electronic population decrease on 5 D_(3) state of Tb^(3+)þare observed by the deformation of adjacent oxygen octahedral structure.Finally,the asprepared SrO:0.01 Tb^(3+)þphosphors,commercial BaMgAl10O17:Eu^(2+)þblue phosphor,and CaAlSiN3:Eu^(2+)þred phosphor are mixed and coated onto 280 nm deep-ultraviolet LED chip to assemble white light-emitting LED device.The LEDs show CCT of 3850 K,4136 K,and 4741 K,with color rendering index of 90.3,90.8,and 92.1,respectively.These insights will advance the fundamental knowledge of crystal engineering in cubic rock salt,and enable new ways to manipulate energy transfer and electronic transition via defects.
基金Project partly supported by the Science Foundation of the Ministry of Education of China(Grant No.30800)the National Natural Science Foundation of China(Grant Nos.11004060 and 11027403)the Shanghai Municipal Science and Technology Commission,China(Grant Nos.10XD1401800,09142200501,09ZR1409300,09JC1404700,and 10JC1404500)
文摘We theoretically and experimentally study the polarization and phase control of two-photon absorption in an isotropic molecular system. We theoretically show that the two-photon transition probability decreases when the laser polarization changes from linear through elliptical to circular, and the laser polarization does not affect the control efficiency of two-photon transition probability by shaping the spectral phase. These theoretical results are experimentally confirmed in coumarin 480. Furthermore, we propose that the combination of the laser polarization with the spectral phase modulation can further increase the control efficiency of the two-photon absorption.
基金supported by National High-Tech Research and Development Program of China under Grant No.2013AA010501
文摘Optical transmission technologies have gone through several generations of development.Spectral efficiency has significant ly improved,and industry has begun to search for an answer to a basic question：What are the fundamental linear and nonlin ear signal channel limitations of the Shannon theory when there is no compensation in an optical fiber transmission system？Next-generation technologies should exceed the 100G transmis sion capability of coherent systems in order to approach the Shannon limit.Spectral efficiency first needs to be improved be fore overall transmission capability can be improved.The means to improve spectral efficiency include more complex modulation formats and channel encoding/decoding algorithms,prefiltering with multisymbol detection,optical OFDM and Ny quist WDM multicarrier technologies,and nonlinearity compen sation.With further optimization,these technologies will most likely be incorporated into beyond-100G optical transport sys tems to meet bandwidth demand.
基金National Natural Science Foundation of China(61975046,62375068)。
文摘Multi-spectral and multi-functional optical components play a crucial role in fields such as high-speed communications and optical sensing.However,the interaction between different spectra and matter varies significantly,making it challenging to simultaneously achieve dynamic multi-spectral modulation capabilities.We designed a modulator based on a planar nested multiscale metasurface,incorporating silicon(Si)and perovskite as control materials,to modulate both microwave and terahertz(THz)ranges.
基金supported by the National Natural Science Foundation of China(Grant Nos.52306078 and 52211530089)Taishan Scholars of Shandong Province(Grant No.tsqn201812105)+1 种基金the Natural Science Foundation of Shandong Province(Grant No.ZR2023QE141)the Royal Society(Grant No.IEC\NSFC\211210)。
文摘Passive daytime radiative cooling(PDRC)technology has great potential in reducing cooling energy consumption.In order to further improve the spectral performance of PDRC coatings,current researchers mostly focus on the selection and size design of functional particles,while ignoring the optical properties enhancement effect caused by the interlayer binder.In this study,based on the principle that the refractive index difference between layers enhanced the backscattering performance of the solar spectrum,we proposed and manufactured a double-layer PDRC coating with polyvinylidene difluoride(PVDF)as the filmforming material in the upper layer and polydimethylsiloxane(PDMS)as the film-forming material in the lower layer,both filled with Al_(2)O_(3) and SiO_(2) particles.The double-layer PDRC coating exhibited excellent spectral performance that a high solar reflectivity of 98%and an emissivity of 0.95 at the“atmospheric window”band.In comparison,the solar spectrum reflectivity of the single-layer PDRC coatings based on PVDF and PDMS of the same thickness was 95%and 94.7%,respectively.Outdoor tests showed that the PDRC coating achieved a temperature decrease of up to 7.1℃ under direct sunlight at noon time.In addition,the PDRC coating had excellent weather resistance,water resistance,and other basic properties.This article opens up a new idea and provides methodological guidance for the design of double-layer PDRC coatings.
