In the context of the prevalent winter air quality issues in China marked by declining PM_(2.5)and rising O_(3),this study employed amodified WRF-Chem model to examine the aerosol radiation interaction(ARI),heterogene...In the context of the prevalent winter air quality issues in China marked by declining PM_(2.5)and rising O_(3),this study employed amodified WRF-Chem model to examine the aerosol radiation interaction(ARI),heterogeneous chemistry(AHC),and their combined impact(ALL)on the variations in O_(3)and PM_(2.5)during the 2014–2020 in eastern China.Our analysis confirmed that ARI curtailed O_(3)while elevating PM_(2.5).AHC reduced O_(3)through heterogeneous absorption of NOx and hydroxideswhile notably fostering fine-grained sulfate,resulting in a PM_(2.5)increase.Emission reductions mitigated the inhibitory impact of ARI on meteorological fields and photolysis rates.Emission reduction individually without aerosol feedback led to a 5.43 ppb O_(3)increase and a 22.89μg/m^(3)PM_(2.5)decrease.ARI and AHC amplified the emission-reduction-induced(ERI)O_(3)rise by 1.83 and 0.31 ppb,respectively.The response of ARI to emission diminution brought about a modest PM_(2.5)increase of 0.31μg/m^(3).Conversely,AHC,acting as the primary contributor,caused a noteworthy PM_(2.5)decrease of 4.60μg/m^(3).As efforts concentrate on reducing PM_(2.5),the promotion of ARI on PM_(2.5)counterbalanced the efficacy of emission reduction and the AHC-induced strengthening of PM_(2.5)decrease.The ALL magnified the ERI O_(3)increase by 38.9%and PM_(2.5)decrease by 18.7%.Sensitivity experiments with different degrees of emission reduction demonstrated a consistent linear relationship between the ALL-induced enhancement of O_(3)increase and PM_(2.5)decrease to the ERI PM_(2.5)decline.Our investigation revealed the complex connection between emissions and aerosol feedback in influencing air quality.展开更多
To obtain the influence rules of the coating parameters of a long-period fiber grating(LPFG)with respect to temperature,strain and refractive index sensing properties,based on the mode coupling theory,a strict four-la...To obtain the influence rules of the coating parameters of a long-period fiber grating(LPFG)with respect to temperature,strain and refractive index sensing properties,based on the mode coupling theory,a strict four-layer theorietical model of a metal film coated LPFG is established,and these parameters that affect the spectral characteristics of the metal film coated LPFG are studied.The simulation results show that there is an optimal metal film thickness on the surface of the LPFG that will induce the surface-plasmon resonance(SP R)effect,which results in higher sensitivity to the environmental temperature and refractive index but has little influence on the strain There is theoretical evidence that when the silver thickness is between0.8and1.2nm,the refractive index sensitivity will reach the peak point of42.4026,at which the refractive index sensor sensitivity is increased by4.S%.The theoretical results of coating a long-period fiber grating provide a good theoretical basis and guidance for LPFG design and parameters optimization展开更多
The study presents a novel source location method based on EEMD （ensemble empirical mode decomposition） and optimized FastICA （independent component analysis） for determining the position of the AE （acoustic emis...The study presents a novel source location method based on EEMD （ensemble empirical mode decomposition） and optimized FastICA （independent component analysis） for determining the position of the AE （acoustic emission） sources in the damage structure of crane. Firstly, The AE signals are self-adaptive decomposed into a number of IMFs （intrinsic mode functions） by using EEMD algorithm. Then, the main feature IMFs signals are extracted as the effective AE source signal by optimized Fast-ICA method, the PSD （power spectral density） of each IMF and the real IMFs are obtained. According to the principle of spectrum similarity, time delay is computed at the different channels in combination with the Cross Correlation time delay estimation principle. Thirdly, a novel source location algorithm based on EEMD-FastICA is proposed and the results of AE source location are obtained. Finally, the three-point bending test for the crane is implemented in order to validate the efficiency of the proposed method. The experimental results indicate that the proposed method has the ability to determinate the position of the AE sources and reduce the interference noises. Moreover, compared with the traditional location algorithm, a considerable improvement is obtained.展开更多
AET （acoustic emission tomography） is a new visualization location method for inspecting and locating the intemal damages in the structures. In this paper, the AET is applied to detect and visualize damage source lo...AET （acoustic emission tomography） is a new visualization location method for inspecting and locating the intemal damages in the structures. In this paper, the AET is applied to detect and visualize damage source locations in the Q235B steel structure to validate its effectiveness. Firstly, the ABAQUS/Explicit simulation model.of the steel structure with one damaged circle in its center is built. And then, the simulated AE signals are obtained to establish the AE tomography. The results show that the damaged circle in the created model can be visualized clearly with the AET in its original location. Finally, the damage source location based on AET is compared with the traditional TOA （time of arrival） location method, and the better location accuracy is obtained. And this fact that further illustrates the AET has a great potential in the application of structure damage detection.展开更多
Sulphate(SO_(4)^(2-))is a main component of PM_(2.5)in China.The chemical formation mechanisms of sulphate are complex,and many air quality models have been used to analyse these mechanisms.To improve the accuracy of ...Sulphate(SO_(4)^(2-))is a main component of PM_(2.5)in China.The chemical formation mechanisms of sulphate are complex,and many air quality models have been used to analyse these mechanisms.To improve the accuracy of Weather Research Forecast-Chemistry(WRF-Chem)on sulphate,an alternative method is proposed in this paper.Moreover,data assimilation is performed to adjust the chemical reaction rates of sulphate.Based on the original reactions,a new sulphate parameterisation scheme,which includes two hypothetical reactions and six undetermined parameters,was added.Based on the WRF-Chem/DART(Data Assistance Research Testbed)system,the near-ground concentrations of SO_(4)^(2-),SO_(2),NO_(2),O_(3)and particulate matter are assimilated to adjust the six parameters.After adjusting the parameters,the new scheme can effectively solve the underestimation of SO_(4)^(2-)and overestimation of SO_(2).The simulation of SO_(4)^(2-)improved as the mean bias changed from-13.1μg m^(-3)to 3.5μg m^(-3)while SO_(2)improved from 17.0μg m^(-3)to 6.3μg m^(-3).The temporal and spatial variation characteristics predicted by the new scheme are consistent with the theoretical research results,indicating that the complex mechanism of sulphate formation could be replaced by the temporal and spatial variation characteristics predicted by the new scheme and that the parameters can be adjusted by data assimilation.Furthermore,the reaction rates of the SO_(4)^(2-)parameterisation scheme of the WRF-Chem model are improved in this study,and a new method for improving the accuracy of the air quality model is provided.展开更多
基金supported by the National Natural Science Foundation of China(No.42077192)the National Key Basic Research&Development Program of China(No.2020YFA0607802).
文摘In the context of the prevalent winter air quality issues in China marked by declining PM_(2.5)and rising O_(3),this study employed amodified WRF-Chem model to examine the aerosol radiation interaction(ARI),heterogeneous chemistry(AHC),and their combined impact(ALL)on the variations in O_(3)and PM_(2.5)during the 2014–2020 in eastern China.Our analysis confirmed that ARI curtailed O_(3)while elevating PM_(2.5).AHC reduced O_(3)through heterogeneous absorption of NOx and hydroxideswhile notably fostering fine-grained sulfate,resulting in a PM_(2.5)increase.Emission reductions mitigated the inhibitory impact of ARI on meteorological fields and photolysis rates.Emission reduction individually without aerosol feedback led to a 5.43 ppb O_(3)increase and a 22.89μg/m^(3)PM_(2.5)decrease.ARI and AHC amplified the emission-reduction-induced(ERI)O_(3)rise by 1.83 and 0.31 ppb,respectively.The response of ARI to emission diminution brought about a modest PM_(2.5)increase of 0.31μg/m^(3).Conversely,AHC,acting as the primary contributor,caused a noteworthy PM_(2.5)decrease of 4.60μg/m^(3).As efforts concentrate on reducing PM_(2.5),the promotion of ARI on PM_(2.5)counterbalanced the efficacy of emission reduction and the AHC-induced strengthening of PM_(2.5)decrease.The ALL magnified the ERI O_(3)increase by 38.9%and PM_(2.5)decrease by 18.7%.Sensitivity experiments with different degrees of emission reduction demonstrated a consistent linear relationship between the ALL-induced enhancement of O_(3)increase and PM_(2.5)decrease to the ERI PM_(2.5)decline.Our investigation revealed the complex connection between emissions and aerosol feedback in influencing air quality.
基金National Natural Science Foundation of China(No.51309001)Scientific Research Key Project of Anhui Province(No.KJ2017A041)
文摘To obtain the influence rules of the coating parameters of a long-period fiber grating(LPFG)with respect to temperature,strain and refractive index sensing properties,based on the mode coupling theory,a strict four-layer theorietical model of a metal film coated LPFG is established,and these parameters that affect the spectral characteristics of the metal film coated LPFG are studied.The simulation results show that there is an optimal metal film thickness on the surface of the LPFG that will induce the surface-plasmon resonance(SP R)effect,which results in higher sensitivity to the environmental temperature and refractive index but has little influence on the strain There is theoretical evidence that when the silver thickness is between0.8and1.2nm,the refractive index sensitivity will reach the peak point of42.4026,at which the refractive index sensor sensitivity is increased by4.S%.The theoretical results of coating a long-period fiber grating provide a good theoretical basis and guidance for LPFG design and parameters optimization
基金Acknowledgments This work is supported by the National Natural Science Foundation of China （51575101, 51305176）, the funds of High-level talents of JIT （JIT6201623, FHXM201608）.
文摘The study presents a novel source location method based on EEMD （ensemble empirical mode decomposition） and optimized FastICA （independent component analysis） for determining the position of the AE （acoustic emission） sources in the damage structure of crane. Firstly, The AE signals are self-adaptive decomposed into a number of IMFs （intrinsic mode functions） by using EEMD algorithm. Then, the main feature IMFs signals are extracted as the effective AE source signal by optimized Fast-ICA method, the PSD （power spectral density） of each IMF and the real IMFs are obtained. According to the principle of spectrum similarity, time delay is computed at the different channels in combination with the Cross Correlation time delay estimation principle. Thirdly, a novel source location algorithm based on EEMD-FastICA is proposed and the results of AE source location are obtained. Finally, the three-point bending test for the crane is implemented in order to validate the efficiency of the proposed method. The experimental results indicate that the proposed method has the ability to determinate the position of the AE sources and reduce the interference noises. Moreover, compared with the traditional location algorithm, a considerable improvement is obtained.
基金Acknowledgments This work is supported by the National Natural Science Foundation of China （No.51575101, No.51305176）, the introduction fund of High-level talents of JIT （No.JIT6201623）. In addition, the author is grateful to the EGWAE reviewers for their future reviewed work.
文摘AET （acoustic emission tomography） is a new visualization location method for inspecting and locating the intemal damages in the structures. In this paper, the AET is applied to detect and visualize damage source locations in the Q235B steel structure to validate its effectiveness. Firstly, the ABAQUS/Explicit simulation model.of the steel structure with one damaged circle in its center is built. And then, the simulated AE signals are obtained to establish the AE tomography. The results show that the damaged circle in the created model can be visualized clearly with the AET in its original location. Finally, the damage source location based on AET is compared with the traditional TOA （time of arrival） location method, and the better location accuracy is obtained. And this fact that further illustrates the AET has a great potential in the application of structure damage detection.
基金supported by the National Key Research and Development Program of China(Grant Nos.2020YFA0607802&2019YFC0214603)。
文摘Sulphate(SO_(4)^(2-))is a main component of PM_(2.5)in China.The chemical formation mechanisms of sulphate are complex,and many air quality models have been used to analyse these mechanisms.To improve the accuracy of Weather Research Forecast-Chemistry(WRF-Chem)on sulphate,an alternative method is proposed in this paper.Moreover,data assimilation is performed to adjust the chemical reaction rates of sulphate.Based on the original reactions,a new sulphate parameterisation scheme,which includes two hypothetical reactions and six undetermined parameters,was added.Based on the WRF-Chem/DART(Data Assistance Research Testbed)system,the near-ground concentrations of SO_(4)^(2-),SO_(2),NO_(2),O_(3)and particulate matter are assimilated to adjust the six parameters.After adjusting the parameters,the new scheme can effectively solve the underestimation of SO_(4)^(2-)and overestimation of SO_(2).The simulation of SO_(4)^(2-)improved as the mean bias changed from-13.1μg m^(-3)to 3.5μg m^(-3)while SO_(2)improved from 17.0μg m^(-3)to 6.3μg m^(-3).The temporal and spatial variation characteristics predicted by the new scheme are consistent with the theoretical research results,indicating that the complex mechanism of sulphate formation could be replaced by the temporal and spatial variation characteristics predicted by the new scheme and that the parameters can be adjusted by data assimilation.Furthermore,the reaction rates of the SO_(4)^(2-)parameterisation scheme of the WRF-Chem model are improved in this study,and a new method for improving the accuracy of the air quality model is provided.
