We report the world-leading performance of a 1.3 GHz cryomodule equipped with eight 9-cell superconducting radio-frequency cavities that underwent a medium-temperature furnace baking process.During continuous wave hor...We report the world-leading performance of a 1.3 GHz cryomodule equipped with eight 9-cell superconducting radio-frequency cavities that underwent a medium-temperature furnace baking process.During continuous wave horizontal testing,these cavities achieved unprecedented average intrinsic quality factors of 4.0×10^(10)at 20 MV/m and 3.2×10^(10)at 29 MV/m,with no instances of field emission.The cryomodule demonstrates near-complete preservation of ultra-high quality factors and ultra-high accelerating gradients from vertical to horizontal testing,marking a significant milestone in continuous-wave superconducting radio-frequency accelerator technology.This letter presents the cryomodule development experience,includ-ing cavity preparation,cryomodule assembly,degaussing,fast cooldown,and performance testing.展开更多
Accurately predicting the powder factor during blasting is essential for sustainable production planning in low-grade mines.This research presents a method for predicting powder factor based on the heterogeneity of ro...Accurately predicting the powder factor during blasting is essential for sustainable production planning in low-grade mines.This research presents a method for predicting powder factor based on the heterogeneity of rock mass rating(RMR).Considering a low-grade metal mine as an example,this study exploited geostatistical methods to obtain independent RMR for each block unit.A three-dimensional spatial distribution model for the powder factor was developed on the basis of the relationships between the RMR and the powder factor.Subsequently,models for blasting cost and mining value were built and employed to optimize the open-pit limit.The multi-variable model based on the RMR performed well in predicting the powder factor,achieving a correlation coefficient of 0.88(root mean square error of 4.3)and considerably outperforming the uniaxial compressive strength model.After model optimization,the mean size and standard deviation of the fragments in the blast pile decreased by 8.5%and 35.1%,respectively,whereas the boulder yield and its standard deviation decreased by 33.3%and 58.8%,respectively.Additionally,optimizing the open-pit limit using this method reduced the amount of rock,increased the amount of ore,and lowered blasting costs,thereby enhancing the economic efficiency of the mine.This study provides valuable insights for blasting design and mining decisions,demonstrating the advantages and potential applications of powder factor prediction based on the heterogeneity of rock mass quality.展开更多
For regional ecological management,it is important to evaluate the quality of ecosystems and analyze the underlying causes of ecological changes.Using the Google Earth Engine(GEE)platform,the remote sensing ecological...For regional ecological management,it is important to evaluate the quality of ecosystems and analyze the underlying causes of ecological changes.Using the Google Earth Engine(GEE)platform,the remote sensing ecological index(RSEI)was calculated for the Lijiang River Basin in Guangxi Zhuang Autonomous Region for 1991,2001,2011,and 2021.Spatial autocorrelation analysis was employed to investigate spatiotemporal variations in the ecological environmental quality of the Lijiang River Basin.Furthermore,geographic detectors were used to quantitatively analyze influencing factors and their interaction effects on ecological environmental quality.The results verified that:1)From 1991 to 2021,the ecological environmental quality of the Lijiang River Basin demonstrated significant improvement.The area with good and excellent ecological environmental quality in proportion increased by 19.69%(3406.57 km^(2)),while the area with fair and poor ecological environmental quality in proportion decreased by 10.76%(1860.36 km^(2)).2)Spatially,the ecological environmental quality of the Lijiang River Basin exhibited a pattern of low quality in the central region and high quality in the periphery.Specifically,poor ecological environmental quality characterized the Guilin urban area,Pingle County,and Lingchuan County.3)From 1991 to 2021,a significant positive spatial correlation was observed in ecological environmental quality of the Lijiang River Basin.Areas with high-high agglomeration were predominantly forests and grasslands,indicating good ecological environmental quality,whereas areas with low-low agglomeration were dominated by cultivated land and construction land,indicating poor ecological environmental quality.4)Annual average precipitation and temperature exerted the most significant influence on the ecological environmental quality of the basin,and their interactions with other factors had the great influence.This study aimed to enhance understanding of the evolution of the ecological environment in the Lijiang River Basin of Guangxi Zhuang Autonomous Region and provide scientific guidance for decision-making and management related to ecology in the region.展开更多
The AFM probe in tapping mode is a continuous process of energy dissipation,from moving away from to intermittent contact with the sample surfaces.At present,studies regarding the energy dissipation mechanism of this ...The AFM probe in tapping mode is a continuous process of energy dissipation,from moving away from to intermittent contact with the sample surfaces.At present,studies regarding the energy dissipation mechanism of this continuous process have only been reported sporadically,and there are no systematic explanations or experimental verifications of the energy dissipation mechanism in each stage of the continuous process.The quality factors can be used to characterize the energy dissipation in TM-AFM systems.In this study,the vibration model of the microcantilever beam was established,coupling the vibration and damping effects of the microcantilever beam.The quality factor of the vibrating microcantilever beam under damping was derived,and the air viscous damping when the probe is away from the sample and the air squeeze film damping when the probe is close to the sample were calculated.In addition,the mechanism of the damping effects of different shapes of probes at different tip–sample distances was analyzed.The accuracy of the theoretical simplified model was verified using both experimental and simulation methods.A clearer understanding of the kinetic characteristics and damping mechanism of the TM-AFM was achieved by examining the air damping dissipation mechanism of AFM probes in the tapping mode,which was very important for improving both the quality factor and the imaging quality of the TM-AFM system.This study’s research findings also provided theoretical references and experimental methods for the future study of the energy dissipation mechanism of micro-nano-electromechanical systems.展开更多
We demonstrated a novel method to measure the unloaded quality factor(Q factor) of high-Q resonant cavities. This method was used to obtain data with low errors and calculate the unloaded Q factor. This procedure was ...We demonstrated a novel method to measure the unloaded quality factor(Q factor) of high-Q resonant cavities. This method was used to obtain data with low errors and calculate the unloaded Q factor. This procedure was more reliable than traditional methods. The data required for the method were near the resonant frequency,not at the half-power points of the reflection coefficient curve or Smith chart. We applied the new method to measure a resonant cavity with an unloaded Q factor of^100,000, obtaining good agreement between the measured and theoretical results.展开更多
Two 650 MHz single-cell superconducting radio-frequency(SRF)cavities used for the Circular Electron Positron Collider(CEPC)were studied to achieve a high accelerating gradient(E_(acc))and high intrinsic quality factor...Two 650 MHz single-cell superconducting radio-frequency(SRF)cavities used for the Circular Electron Positron Collider(CEPC)were studied to achieve a high accelerating gradient(E_(acc))and high intrinsic quality factor(Q_(0)).The 650 MHz single-cell cavities were subjected to a combination of buffered chemical polishing(BCP)and electropolishing(EP),and their E_(acc) exceeded40 MV/m.Such a high E_(acc) may result from the cold EP with more uniform removal.BCP is easy,cheap,and rough,whereas EP is complicated,expensive,and precise Therefore,the combination of BCP and EP investigated in this study is suitable for surface treatments of mass SRF cavities.Medium temperature(mid-T)furnace baking was also conducted,which demonstrated an ultrahigh Q_(0) of 8×10^(10) at 22 MV/m for both cavities,and an extremely low BCS resistance(R_(BCS))of~1.0 nΩwas achieved a2.0 K.展开更多
Five factors expressing greenbelt quality and one factor expressing quantity were adopted for evaluation of the residential greenbelt, and the AHP （Analytical Hierarchy Process） method was used to determine the valu...Five factors expressing greenbelt quality and one factor expressing quantity were adopted for evaluation of the residential greenbelt, and the AHP （Analytical Hierarchy Process） method was used to determine the value of factors. Thirty residential areas were selected as the samples. Two principal components were extracted and their expression was constructed by method of factor anlysis, therefore, quality evaluation of residential greenbelt was obtained. The accuracy of the function and implement quality classification toward the residential greenbelts in Xinxiang City were validated by clustering analysis method. The results showed that the greenbelt quality of fourteen residential areas was higher than the average level, of which eleven were newly-built residential areas. The 30 residential areas were classified into three types according to their greenbelt features and their formation by clustering analysis method. Finally rational proposal basing on aforesaid evaluating results was proposed for construction and renewal of residential greenbelt, upon which directive basis was provided for construction and renewal of residential greenbelt.展开更多
This paper proposes an improved design of micromachined tuning fork gyroscope （M-TFG） to decouple the cross talk between driving and sensing directions better and to increase resolution. By employing dual-folds spri...This paper proposes an improved design of micromachined tuning fork gyroscope （M-TFG） to decouple the cross talk between driving and sensing directions better and to increase resolution. By employing dual-folds spring suspension, the drive mode and the sense mode are mechanically decoupled. Through careful layout design of the location of the dual-folds spring suspension and the drive combs, the mechanical coupling effect is further decreased by isolating the unwanted excitation from detection. The quality factor investigation demonstrates that high quality factor can be attained by using this structure, which can bring in accurate resolution. As a result, this design has the potential to accomplish low bias drift and accurate resolution for initial level applications.展开更多
In order to significantly improve the absorption efficiency of monolayer molybdenum disulfide(M-MoS_(2)), an ultranarrowband M-MoS_(2)metamaterial absorber was obtained through theoretical analysis and numerical calcu...In order to significantly improve the absorption efficiency of monolayer molybdenum disulfide(M-MoS_(2)), an ultranarrowband M-MoS_(2)metamaterial absorber was obtained through theoretical analysis and numerical calculation using the finite difference time domain method. The physical mechanism can be better analyzed through critical coupling and guided mode resonance. Its absorption rate at λ = 806.41 nm is as high as 99.8%, which is more than 12 times that of bare MMoS_(2). From the simulation results, adjusting the geometric parameters of the structure can control the resonant wavelength range of the M-MoS_(2). In addition, we also found that the maximum quality factor is 1256.8. The numerical result shows that the design provides new possibilities for ultra-narrowband M-MoS_(2) perfect absorbers in the near-infrared spectrum.The results of this work indicate that the designed structure has excellent prospects for application in wavelength-selective photoluminescence and photodetection.展开更多
The accurate measurement of parameters such as the cavity-loaded quality factor(Q_(L))and half bandwidth(f_(0.5))is essential for monitoring the performance of superconducting radio-frequency cavities.However,the conv...The accurate measurement of parameters such as the cavity-loaded quality factor(Q_(L))and half bandwidth(f_(0.5))is essential for monitoring the performance of superconducting radio-frequency cavities.However,the conventional"field decay method"employed to calibrate these values requires the cavity to satisfy a"zero-input"condition.This can be challenging when the source impedance is mismatched and produce nonzero forward signals(V_(f))that significantly affect the measurement accuracy.To address this limitation,we developed a modified version of the"field decay method"based on the cavity differential equation.The proposed approach enables the precise calibration of f_(0.5) even under mismatch conditions.We tested the proposed approach on the SRF cavities of the Chinese Accelerator-Driven System Front-End Demo Superconducting Linac and compared the results with those obtained from a network analyzer.The two sets of results were consistent,indicating the usefulness of the proposed approach.展开更多
Low quality(Q) factor is often the limiting factor for high performance carbon nanotube(CNT) resonators. The most commonly used approach to enhance the Q factor of CNTs is to reduce/eliminate the intrinsic defects.Her...Low quality(Q) factor is often the limiting factor for high performance carbon nanotube(CNT) resonators. The most commonly used approach to enhance the Q factor of CNTs is to reduce/eliminate the intrinsic defects.Herein, we show surprisingly that hole defects of suitable size and position are able to enhance the Q factor of CNT, which strongly contradicts to the common notion that the presence of defects promote intrinsic dissipation via defects dissipation. By analyzing the strain distribution, we find that such abnormal enhancement in Q factor of defected CNT originates from a coupling competition mechanism between the atomic mismatch around defected atoms and the thermoelastic damping. Although the presence of holes will introduce an additional defect dissipation source, suitable holes are capable of reducing the energy dissipation arisen from the thermoelastic damping, through changing the spatial strain field of defected CNT. This coupling competition mechanism provides a new route for designing high performance CNT resonators via defects engineering.展开更多
The estimation of the external quality factor is important for designing coupling devices for the cavities.A new representation of the external quality factor calculations for single-cell cavity coupled to a coaxial t...The estimation of the external quality factor is important for designing coupling devices for the cavities.A new representation of the external quality factor calculations for single-cell cavity coupled to a coaxial transmission line is derived based on analytic analysis and numeric analysis with the help of 3D electromagnetic code,and verified with experimental measurements at room temperature.In logarithmic scale the results for the external quality factor were quasi-linear over the limited range,and the simulated and measured data could be used and extrapolated to the superconducting case.For the unpolished 1.5 GHz 3rd harmonic superconducting cavity,the discrepancy between the evaluation value and measurement result is less than 25% within an acceptable deviation.展开更多
The applicable condition of single-frequency laser beam quality factor M^2 is studied. Any real single-frequency laser beam can be classified as Gaussian mode and non-Gaussian mode according to the transverse field di...The applicable condition of single-frequency laser beam quality factor M^2 is studied. Any real single-frequency laser beam can be classified as Gaussian mode and non-Gaussian mode according to the transverse field distribution. Non-Gaussian transverse field distribution can be analytically expressed as the sum of Hermite-Gaussian functions. The propagation function and M^2 factor expression for non-Gaussian mode can be obtained by the second moment definition of laser beam spot. The analytical results show, the same as that of Gaussian mode, that the propagation function follows the hyperbolic law and the value of M^2 factor is a constant for non-Gaussian mode. But, different non-Gaussian field distributions may have the same M^2 value. That means M^2 factor cannot reflect the quality of non-Gaussian laser beams correctly. We conclude that the M^2 factor is applicable only to ideal Gaussian laser beam generated by stable resonators.展开更多
Based on the present coupled mode theory of the photonic crystal resonator array in this paper, we propose a novel side-coupled waveguide to achieve highly efficient coupling of photonic crystal devices. It is found t...Based on the present coupled mode theory of the photonic crystal resonator array in this paper, we propose a novel side-coupled waveguide to achieve highly efficient coupling of photonic crystal devices. It is found that the coupling efficiency is sensitive to the interval, the total number and the quality factor of the resonator. Considering the coupling efficiency and the coupling region, we select five resonators with an interval of six lattice periods. By optimizing the structure parameters of the waveguide and resonator, the quality factors of the resonator can be modulated and the coupling efficiency of the side-coupled waveguide reaches 95.47% in theory. Compared with other coupling methods, the side-coupled waveguide can realize efficient coupling with a compact structure, a high level of integration and a low degree of operational difficulties.展开更多
Reservoir quality varies greatly in the Shahejie Formation in the Dongying Sag. It is essential to analyze the variation and mechanisms of reservoir quality for determining the controlling factors based on cores, poro...Reservoir quality varies greatly in the Shahejie Formation in the Dongying Sag. It is essential to analyze the variation and mechanisms of reservoir quality for determining the controlling factors based on cores, porosity measurements and fluid inclusion techniques and so on. The sandstones in the fluvial, （fan） delta-front have the best reservoir quality due to the depositional conditions mechanically controlling the petrology configuration and the primary porosity, and chemically influencing the diagenesis and development of secondary pores. The activity of the boundary faults and the sedimentary facies dominate the variation of reservoir quality in different areas and intervals. The reservoir quality varies with the position of sandstone beds in different vertical models of sandstone and mudstone. This mainly arose from the strong cementation or strong dissolution in the sandstone caused by the diagenesis evolution of adjacent mudstone. With higher oil saturation reservoir quality is better because the hydrocarbon charge favors dissolution and restricts cementation. Diagenesis, depositional conditions and tectonic setting are the key controls of reservoir quality in the Shahejie Formation of the Dongying Sag.展开更多
基金supported by Zhangjiang Laboratory,the SHINE R&D project(No.2017SHZDZX02)the SHINE projectthe National Natural Science Foundation of China(No.12125508).
文摘We report the world-leading performance of a 1.3 GHz cryomodule equipped with eight 9-cell superconducting radio-frequency cavities that underwent a medium-temperature furnace baking process.During continuous wave horizontal testing,these cavities achieved unprecedented average intrinsic quality factors of 4.0×10^(10)at 20 MV/m and 3.2×10^(10)at 29 MV/m,with no instances of field emission.The cryomodule demonstrates near-complete preservation of ultra-high quality factors and ultra-high accelerating gradients from vertical to horizontal testing,marking a significant milestone in continuous-wave superconducting radio-frequency accelerator technology.This letter presents the cryomodule development experience,includ-ing cavity preparation,cryomodule assembly,degaussing,fast cooldown,and performance testing.
基金supported by the National Key Research and Development Program of China(No.2022YFC2903902)the National Natural Science Foundation of China(Nos.52204080and 52174070)the Fundamental Research Funds for the Central Universities of China(No.2023GFYD17)。
文摘Accurately predicting the powder factor during blasting is essential for sustainable production planning in low-grade mines.This research presents a method for predicting powder factor based on the heterogeneity of rock mass rating(RMR).Considering a low-grade metal mine as an example,this study exploited geostatistical methods to obtain independent RMR for each block unit.A three-dimensional spatial distribution model for the powder factor was developed on the basis of the relationships between the RMR and the powder factor.Subsequently,models for blasting cost and mining value were built and employed to optimize the open-pit limit.The multi-variable model based on the RMR performed well in predicting the powder factor,achieving a correlation coefficient of 0.88(root mean square error of 4.3)and considerably outperforming the uniaxial compressive strength model.After model optimization,the mean size and standard deviation of the fragments in the blast pile decreased by 8.5%and 35.1%,respectively,whereas the boulder yield and its standard deviation decreased by 33.3%and 58.8%,respectively.Additionally,optimizing the open-pit limit using this method reduced the amount of rock,increased the amount of ore,and lowered blasting costs,thereby enhancing the economic efficiency of the mine.This study provides valuable insights for blasting design and mining decisions,demonstrating the advantages and potential applications of powder factor prediction based on the heterogeneity of rock mass quality.
基金supported by the Guangxi Natural Science Foundation(2020GXNSFAA297266)Doctoral Research Foundation of Guilin University of Technology(GUTQDJJ2007059)Guangxi Hidden Metallic Mineral Exploration Key Laboratory。
文摘For regional ecological management,it is important to evaluate the quality of ecosystems and analyze the underlying causes of ecological changes.Using the Google Earth Engine(GEE)platform,the remote sensing ecological index(RSEI)was calculated for the Lijiang River Basin in Guangxi Zhuang Autonomous Region for 1991,2001,2011,and 2021.Spatial autocorrelation analysis was employed to investigate spatiotemporal variations in the ecological environmental quality of the Lijiang River Basin.Furthermore,geographic detectors were used to quantitatively analyze influencing factors and their interaction effects on ecological environmental quality.The results verified that:1)From 1991 to 2021,the ecological environmental quality of the Lijiang River Basin demonstrated significant improvement.The area with good and excellent ecological environmental quality in proportion increased by 19.69%(3406.57 km^(2)),while the area with fair and poor ecological environmental quality in proportion decreased by 10.76%(1860.36 km^(2)).2)Spatially,the ecological environmental quality of the Lijiang River Basin exhibited a pattern of low quality in the central region and high quality in the periphery.Specifically,poor ecological environmental quality characterized the Guilin urban area,Pingle County,and Lingchuan County.3)From 1991 to 2021,a significant positive spatial correlation was observed in ecological environmental quality of the Lijiang River Basin.Areas with high-high agglomeration were predominantly forests and grasslands,indicating good ecological environmental quality,whereas areas with low-low agglomeration were dominated by cultivated land and construction land,indicating poor ecological environmental quality.4)Annual average precipitation and temperature exerted the most significant influence on the ecological environmental quality of the basin,and their interactions with other factors had the great influence.This study aimed to enhance understanding of the evolution of the ecological environment in the Lijiang River Basin of Guangxi Zhuang Autonomous Region and provide scientific guidance for decision-making and management related to ecology in the region.
基金the National Natural Science Foun-dation of China(Grant No.11572031).
文摘The AFM probe in tapping mode is a continuous process of energy dissipation,from moving away from to intermittent contact with the sample surfaces.At present,studies regarding the energy dissipation mechanism of this continuous process have only been reported sporadically,and there are no systematic explanations or experimental verifications of the energy dissipation mechanism in each stage of the continuous process.The quality factors can be used to characterize the energy dissipation in TM-AFM systems.In this study,the vibration model of the microcantilever beam was established,coupling the vibration and damping effects of the microcantilever beam.The quality factor of the vibrating microcantilever beam under damping was derived,and the air viscous damping when the probe is away from the sample and the air squeeze film damping when the probe is close to the sample were calculated.In addition,the mechanism of the damping effects of different shapes of probes at different tip–sample distances was analyzed.The accuracy of the theoretical simplified model was verified using both experimental and simulation methods.A clearer understanding of the kinetic characteristics and damping mechanism of the TM-AFM was achieved by examining the air damping dissipation mechanism of AFM probes in the tapping mode,which was very important for improving both the quality factor and the imaging quality of the TM-AFM system.This study’s research findings also provided theoretical references and experimental methods for the future study of the energy dissipation mechanism of micro-nano-electromechanical systems.
基金supported by the National Key Research and Development Program of China(No.2016YFA0401902)
文摘We demonstrated a novel method to measure the unloaded quality factor(Q factor) of high-Q resonant cavities. This method was used to obtain data with low errors and calculate the unloaded Q factor. This procedure was more reliable than traditional methods. The data required for the method were near the resonant frequency,not at the half-power points of the reflection coefficient curve or Smith chart. We applied the new method to measure a resonant cavity with an unloaded Q factor of^100,000, obtaining good agreement between the measured and theoretical results.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB25000000)the National Natural Science Foundation of China(No.12075270)the Platform of Advanced Photon Source Technology R&D。
文摘Two 650 MHz single-cell superconducting radio-frequency(SRF)cavities used for the Circular Electron Positron Collider(CEPC)were studied to achieve a high accelerating gradient(E_(acc))and high intrinsic quality factor(Q_(0)).The 650 MHz single-cell cavities were subjected to a combination of buffered chemical polishing(BCP)and electropolishing(EP),and their E_(acc) exceeded40 MV/m.Such a high E_(acc) may result from the cold EP with more uniform removal.BCP is easy,cheap,and rough,whereas EP is complicated,expensive,and precise Therefore,the combination of BCP and EP investigated in this study is suitable for surface treatments of mass SRF cavities.Medium temperature(mid-T)furnace baking was also conducted,which demonstrated an ultrahigh Q_(0) of 8×10^(10) at 22 MV/m for both cavities,and an extremely low BCS resistance(R_(BCS))of~1.0 nΩwas achieved a2.0 K.
基金supported by the Science and Technology Project of Henan Provincial Science and Technology Department (No.0424490012 )Major Program of Henan Institute of Science and Technology (No.040132)
文摘Five factors expressing greenbelt quality and one factor expressing quantity were adopted for evaluation of the residential greenbelt, and the AHP （Analytical Hierarchy Process） method was used to determine the value of factors. Thirty residential areas were selected as the samples. Two principal components were extracted and their expression was constructed by method of factor anlysis, therefore, quality evaluation of residential greenbelt was obtained. The accuracy of the function and implement quality classification toward the residential greenbelts in Xinxiang City were validated by clustering analysis method. The results showed that the greenbelt quality of fourteen residential areas was higher than the average level, of which eleven were newly-built residential areas. The 30 residential areas were classified into three types according to their greenbelt features and their formation by clustering analysis method. Finally rational proposal basing on aforesaid evaluating results was proposed for construction and renewal of residential greenbelt, upon which directive basis was provided for construction and renewal of residential greenbelt.
基金supported by the 11th Five-Year Plan Military Pre-study Foundation under Grand No. G17010801TX11030203
文摘This paper proposes an improved design of micromachined tuning fork gyroscope （M-TFG） to decouple the cross talk between driving and sensing directions better and to increase resolution. By employing dual-folds spring suspension, the drive mode and the sense mode are mechanically decoupled. Through careful layout design of the location of the dual-folds spring suspension and the drive combs, the mechanical coupling effect is further decreased by isolating the unwanted excitation from detection. The quality factor investigation demonstrates that high quality factor can be attained by using this structure, which can bring in accurate resolution. As a result, this design has the potential to accomplish low bias drift and accurate resolution for initial level applications.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11604311, 61705204, and 21506257)the Scientific Research Fund of Si Chuan Provincial Science and Technology Department, China (Grant Nos. 2020YJ0137 and 2020YFG0467)+1 种基金the National Defense Science and Technology Innovation Special Zone Project of China (Grant No. 19-163-21-TS-001-067-01)the College Students’s Innovation and Entrepreneurship Training Program (Grant No. S202110619065)。
文摘In order to significantly improve the absorption efficiency of monolayer molybdenum disulfide(M-MoS_(2)), an ultranarrowband M-MoS_(2)metamaterial absorber was obtained through theoretical analysis and numerical calculation using the finite difference time domain method. The physical mechanism can be better analyzed through critical coupling and guided mode resonance. Its absorption rate at λ = 806.41 nm is as high as 99.8%, which is more than 12 times that of bare MMoS_(2). From the simulation results, adjusting the geometric parameters of the structure can control the resonant wavelength range of the M-MoS_(2). In addition, we also found that the maximum quality factor is 1256.8. The numerical result shows that the design provides new possibilities for ultra-narrowband M-MoS_(2) perfect absorbers in the near-infrared spectrum.The results of this work indicate that the designed structure has excellent prospects for application in wavelength-selective photoluminescence and photodetection.
基金supported by the project of Large Research Infrastructures"China initiative Accelerator-Driven System"(No.2017-000052-75-01-000590)"Studies of intelligent LLRF control algorithms for superconducting RF cavities"(No.E129851YR0)the National Natural Science Foundation of China(No.12205344).
文摘The accurate measurement of parameters such as the cavity-loaded quality factor(Q_(L))and half bandwidth(f_(0.5))is essential for monitoring the performance of superconducting radio-frequency cavities.However,the conventional"field decay method"employed to calibrate these values requires the cavity to satisfy a"zero-input"condition.This can be challenging when the source impedance is mismatched and produce nonzero forward signals(V_(f))that significantly affect the measurement accuracy.To address this limitation,we developed a modified version of the"field decay method"based on the cavity differential equation.The proposed approach enables the precise calibration of f_(0.5) even under mismatch conditions.We tested the proposed approach on the SRF cavities of the Chinese Accelerator-Driven System Front-End Demo Superconducting Linac and compared the results with those obtained from a network analyzer.The two sets of results were consistent,indicating the usefulness of the proposed approach.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51605172 and 51775201)the Natural Science Foundation of Hubei Province (Grant No. 2016CFB191)+1 种基金the Fundamental Research Funds for the Central Universities (Grant No. 2015MS014)the Hong Kong Scholars Program (No. XJ2020043)。
文摘Low quality(Q) factor is often the limiting factor for high performance carbon nanotube(CNT) resonators. The most commonly used approach to enhance the Q factor of CNTs is to reduce/eliminate the intrinsic defects.Herein, we show surprisingly that hole defects of suitable size and position are able to enhance the Q factor of CNT, which strongly contradicts to the common notion that the presence of defects promote intrinsic dissipation via defects dissipation. By analyzing the strain distribution, we find that such abnormal enhancement in Q factor of defected CNT originates from a coupling competition mechanism between the atomic mismatch around defected atoms and the thermoelastic damping. Although the presence of holes will introduce an additional defect dissipation source, suitable holes are capable of reducing the energy dissipation arisen from the thermoelastic damping, through changing the spatial strain field of defected CNT. This coupling competition mechanism provides a new route for designing high performance CNT resonators via defects engineering.
基金Supported by project Science and Technology Commission of Shanghai Municipality (026505027, 036505011)
文摘The estimation of the external quality factor is important for designing coupling devices for the cavities.A new representation of the external quality factor calculations for single-cell cavity coupled to a coaxial transmission line is derived based on analytic analysis and numeric analysis with the help of 3D electromagnetic code,and verified with experimental measurements at room temperature.In logarithmic scale the results for the external quality factor were quasi-linear over the limited range,and the simulated and measured data could be used and extrapolated to the superconducting case.For the unpolished 1.5 GHz 3rd harmonic superconducting cavity,the discrepancy between the evaluation value and measurement result is less than 25% within an acceptable deviation.
文摘The applicable condition of single-frequency laser beam quality factor M^2 is studied. Any real single-frequency laser beam can be classified as Gaussian mode and non-Gaussian mode according to the transverse field distribution. Non-Gaussian transverse field distribution can be analytically expressed as the sum of Hermite-Gaussian functions. The propagation function and M^2 factor expression for non-Gaussian mode can be obtained by the second moment definition of laser beam spot. The analytical results show, the same as that of Gaussian mode, that the propagation function follows the hyperbolic law and the value of M^2 factor is a constant for non-Gaussian mode. But, different non-Gaussian field distributions may have the same M^2 value. That means M^2 factor cannot reflect the quality of non-Gaussian laser beams correctly. We conclude that the M^2 factor is applicable only to ideal Gaussian laser beam generated by stable resonators.
基金Project supported by the National Natural Science Foundation of China (Grant No. 60877031)
文摘Based on the present coupled mode theory of the photonic crystal resonator array in this paper, we propose a novel side-coupled waveguide to achieve highly efficient coupling of photonic crystal devices. It is found that the coupling efficiency is sensitive to the interval, the total number and the quality factor of the resonator. Considering the coupling efficiency and the coupling region, we select five resonators with an interval of six lattice periods. By optimizing the structure parameters of the waveguide and resonator, the quality factors of the resonator can be modulated and the coupling efficiency of the side-coupled waveguide reaches 95.47% in theory. Compared with other coupling methods, the side-coupled waveguide can realize efficient coupling with a compact structure, a high level of integration and a low degree of operational difficulties.
基金financially supported by the National Natural Science Foundation of China (Grant No. ZX20130157)Science Foundation of China University of Petroleum, Beijing (Grant No. KYJJ2012-01-29)the Key Technologies Research and Development Program of the Chinese Tenth Five-Year Plan (Grant No. 2001BA605A-09)
文摘Reservoir quality varies greatly in the Shahejie Formation in the Dongying Sag. It is essential to analyze the variation and mechanisms of reservoir quality for determining the controlling factors based on cores, porosity measurements and fluid inclusion techniques and so on. The sandstones in the fluvial, （fan） delta-front have the best reservoir quality due to the depositional conditions mechanically controlling the petrology configuration and the primary porosity, and chemically influencing the diagenesis and development of secondary pores. The activity of the boundary faults and the sedimentary facies dominate the variation of reservoir quality in different areas and intervals. The reservoir quality varies with the position of sandstone beds in different vertical models of sandstone and mudstone. This mainly arose from the strong cementation or strong dissolution in the sandstone caused by the diagenesis evolution of adjacent mudstone. With higher oil saturation reservoir quality is better because the hydrocarbon charge favors dissolution and restricts cementation. Diagenesis, depositional conditions and tectonic setting are the key controls of reservoir quality in the Shahejie Formation of the Dongying Sag.
