Resonance enhancement has been increasingly employed in the emergent felntosecond stimu- lated Raman spectroscopy （FSRS） to selectively monitor molecular structure and dynamics with improved spectral and temporal re...Resonance enhancement has been increasingly employed in the emergent felntosecond stimu- lated Raman spectroscopy （FSRS） to selectively monitor molecular structure and dynamics with improved spectral and temporal resolutions and signal-to-noise ratios. Such joint eflforts by the technique- and application-oriented scientists and engineers have laid the foundation for exploiting the tunable FSRS methodology to investigate a great variety of photosensitive systems and elucidate the underlying functional mechanisms on molecular time scales. Dur- ing spectral analysis, peak line shapes remain a major concern with an intricate dependence on resonance conditions. Here, we present a comprehensive study of line shapes by tuning the Rarnan pump wavelength from red to blue side of the ground-state absorption band of the fluorescent dye rhodarnine 6G in solution. Distinct line shape patterns in Stokes and anti-Stokes FSRS as well as from the low to high-frequency modes highlight the competition between multiple third-order and higher-order nonlinear pathways, governed by difl^rent res- onance conditions achieved by Raman pump and probe pulses. In particular, the resonance condition of probe wavelength is revealed to play an important role in generating circular line shape changes through oppositely phased dispersion via hot luminescence （HL） pathways. Meanwhile, on-resonance conditions of the Rarnan pump could promote excited-state vibrational modes which are broadened and red-shifted from the coincident ground-state vibrational modes, posing challenges for spectral analysis. Certain strategies in tuning the Raman pump and probe to characteristic regions across an electronic transition band are discussed to improve the FSRS usability and versatility as a powerful structural dynamics toolset to advance chemical, physical, materials, and biological sciences.展开更多
We numerically investigate a coupled-resonator structure consisting of a stub resonator and a nanodisk resonator using a two-dimensional finite element method. Simulation results show that plasmon-induced transparency...We numerically investigate a coupled-resonator structure consisting of a stub resonator and a nanodisk resonator using a two-dimensional finite element method. Simulation results show that plasmon-induced transparency （PIT） occurs in the transmission spectra, and the sharp asymmetric Fano lines increase the sensitivity to 1.4 ×10^3 nm/RIU. We also analyze the properties of the structure with different radii of the nanodisk and the length of the tooth cavity. Moreover, we find that the PIP only happens when the staggered system is around a fixed location with different separate distances, which is not similar to the previous researches. Our model may be important to photonic-integrated circuits and the sensitivity in sensors.展开更多
Color centers play key roles in,e.g.,solid state lighting and quantum information technology.Here,we describe an approach for predicting the optical line shapes of such emitters based on direct sampling of the underly...Color centers play key roles in,e.g.,solid state lighting and quantum information technology.Here,we describe an approach for predicting the optical line shapes of such emitters based on direct sampling of the underlying autocorrelation functions through molecular dynamics simulations(MD-ACF).The energy landscapes are represented by a machine-learned potential that describes both the ground and excited state landscapes through a single model,guaranteeing size-consistent predictions.We apply this methodology to the(V_(Si)V_(C))_(kk)^(0)divacancy defect in 4H-SiC and demonstrate that at low temperatures,the present MD-ACF approach reproduces results from the traditional generating function approach.Unlike the latter,it is,however,also applicable at high temperatures as it avoids harmonic and parallel-mode approximations and can be applied to study non-crystalline materials.The MD-ACF methodology thus promises to substantially widen the range of computational predictions of the optical properties of color centers and related defects.展开更多
Ultrafast extreme ultraviolet (XUV) transient absorption spectroscopy measures the time- and frequencydependent light losses after light–matter interactions. In the linear region, the matter response to an XUV light ...Ultrafast extreme ultraviolet (XUV) transient absorption spectroscopy measures the time- and frequencydependent light losses after light–matter interactions. In the linear region, the matter response to an XUV light field is usually determined by the complex refractive index ̃n. The absorption signal is directly related to the imaginary part of ̃n, namely, the absorption index. The real part of ̃n refers to the real refractive index, which describes the chromatic dispersion of an optical material. However, the real refractive index information is usually not available in conventional absorption experiments. Here, we investigate the refractive index line shape in ultrafast XUV transient absorption spectroscopy by using a scheme that the XUV pulse traverses the target gas jet off-center. The jet has a density gradient in the direction perpendicular to the gas injection direction, which induces deflection on the XUV radiation. Our experimental and theoretical results show that the shape of the frequency-dependent XUV deflection spectra reproduces the refractive index line profile. A typical dispersive refractive index line shape is measured for a single-peak absorption;an additional shoulder structure appears for a doublet absorption.Moreover, the refractive index line shape is controlled by introducing a later-arrived near-infrared pulse to modify the phase of the XUV free induction decay, resulting in different XUV deflection spectra. The results promote our understanding of matter-induced absorption and deflection in ultrafast XUV spectroscopy.展开更多
The line shapes to observe ηc in charmonium transitions, i.e., ψ（2S）, J/ψ→γηc, are investigated. The ηc line shapes in exclusive decays or by observing the inclusive photon spectrum are given. The sensitiviti...The line shapes to observe ηc in charmonium transitions, i.e., ψ（2S）, J/ψ→γηc, are investigated. The ηc line shapes in exclusive decays or by observing the inclusive photon spectrum are given. The sensitivities to measure the ηc resonance parameters are also evaluated. With more than two thousand ηc events observed, the precision of the ηc decay width measurement will be improved by better than 3%. However, the uncertainties associated with the ηc modified line shapes will dominate the systematic errors and this will prohibit precision mass and width measurements.展开更多
The attosecond extreme ultraviolet(XUV) pulse pump and femtosecond infrared(IR) pulse probe scheme is commonly used to study the dynamics and attosecond transient absorption(ATA) spectra of microscopic systems. In a r...The attosecond extreme ultraviolet(XUV) pulse pump and femtosecond infrared(IR) pulse probe scheme is commonly used to study the dynamics and attosecond transient absorption(ATA) spectra of microscopic systems. In a recent report [Proc. Natl. Acad. Sci. USA 121 e2307836121(2024)], we showed that shaped XUV pulses with spectral minima can significantly alter the absorption line shape of helium's 2s2p doubly excited state within a few tens of attoseconds.However, it remains unclear if similar effects could be observed in a singly excited state. In this study, we use shaped XUV pulses to excite helium's 2p singly excited state and couple the 2p and 3d states with a delayed IR pulse. Comparing these results with those from Gaussian XUV pulses, we find that the ATA spectra for the shaped XUV pulses exhibit more pronounced changes with delay, while the changes for the Gaussian pulses are gradual. We also explain these differences through population changes and analytical models. Our findings show that shaped XUV pulses can regulate the dynamics and absorption spectra of a singly excited state.展开更多
We present the design and the experimental demonstration of an invisible cloak with irregular shape by using tensor transmission line（TL） metamaterials. The fabricated cloak consists of tensor TL unit cells exhibiti...We present the design and the experimental demonstration of an invisible cloak with irregular shape by using tensor transmission line（TL） metamaterials. The fabricated cloak consists of tensor TL unit cells exhibiting anisotropic effective material parameters, while the background medium consists of isotropic TL unit cells. The simulated and the measured field patterns around the cloak show a fairly good agreement, both demonstrate that the fabricated cloak can shield the cloaked interior area from electromagnetic fields without perturbing the external fields. The scattering of the cloaked perfect electric conductor（PEC） is minimized. Furthermore, the nonresonant property of the TL structure results in a relatively broad bandwidth of the realized cloak, which is clearly observed in our experiment.展开更多
The study on a miniaturized, low-voltage, wide-bandwidth, high-efficiency modified V-shaped microstrip meander-line slow-wave structure is presented. This structure is evolved from the original U-shaped microstrip mea...The study on a miniaturized, low-voltage, wide-bandwidth, high-efficiency modified V-shaped microstrip meander-line slow-wave structure is presented. This structure is evolved from the original U-shaped microstrip meander-line slow-wave structure, combining the advantages of a traditional microstrip and a rectangular helix. In this paper, simulations of the electromagnetic characteristics and the beam-wave interaction of this structure are carried out. Our study shows that when the design voltage and the current of a sheet electron beam are set to be 4700 V and 100 mA, respectively, this miniature millimeter-wave power amplifier is capable of delivering 160-W output power with a corresponding gain of 37.3 dB and a maximum interaction efficiency of 34% at 97 GHz.展开更多
The influences of different buffer gas, neon and helium, on 199^Hg^＋ clock transition are compared in trapped 199^Hg^＋ linear trap. By the technique of time domain＇s Ramsey separated oscillatory fields, the buffer...The influences of different buffer gas, neon and helium, on 199^Hg^＋ clock transition are compared in trapped 199^Hg^＋ linear trap. By the technique of time domain＇s Ramsey separated oscillatory fields, the buffer gas pressure frequency shifts of 199^Hg^＋ clock transition are measured to be （df/dPNe）（1/f） = 1.8 × 10^-8 Torr^-1 for neon and （df/dPHe） （1/f） = 9.1 × 10^-8 Torr^-1 for helium. Meanwhile, the line-width of 199^Hg^＋ clock transition spectrum with the buffer gas neon is narrower than that with helium at the same pressure. These experimental results show that neon is a more suitable buffer gas than helium in 199^Hg^＋ ions microwave frequency standards because of the 199^Hg^＋ clock transition is less sensitive to neon variations and the better cooling effect of neon. The optimum operating pressure for neon is found to be about 1.0 × 10^-5 Torr in our linear ion trap system.展开更多
We propose a technique to precisely measure the line width of the photoassociation spectra of the excited cesium molecule by using a frequency shifter to generate two laser beams with a precise frequency difference. A...We propose a technique to precisely measure the line width of the photoassociation spectra of the excited cesium molecule by using a frequency shifter to generate two laser beams with a precise frequency difference. A series of photoassociation （PA） spectra are recorded with two laser beam induced molecular lines, whose peak separation serves as an accurate frequency ruler to measure the line width of the PA spectra. The full width half maximum line width was studied as a function of PA laser intensity. The extrapolated value at zero laser intensity is （34.8± 0.22） MHz. By analyzing other broadening mechanisms, a value of （32.02 ± 0.70） MHz was deduced. It is shown that this scheme is inexpensive, simple, robust, and is promising for applications in a variety of other atomic species.展开更多
NMR spectra acquired with experiments using frequency-sweeps such as the wide-band uniform-rate smooth truncation(WURST)spin-echo and Carr-Purcell-Meiboom-Gill(CPMG)sequences cannot be absorptively phased by using onl...NMR spectra acquired with experiments using frequency-sweeps such as the wide-band uniform-rate smooth truncation(WURST)spin-echo and Carr-Purcell-Meiboom-Gill(CPMG)sequences cannot be absorptively phased by using only conventional zerothand first-order phase correction.Implementation of phase correction up to the secondorder is described for obtaining absorptive spectra,which have more desirable line shapes and noise properties than magnitude spectra.The relationship of the second-order phase to the parameters of frequency sweeps is derived.The second-order phasing in the frequency-domain is equivalent to a point spread in the time-domain signal.The application of second-order phase correction is demonstrated with a wideline 35Cl CPMG spikelet spectrum.展开更多
Main cable line shape measurement and parameter identification are a critical task in the construction monitoring and service maintenance of suspension bridges.3D LiDAR scanning can simultaneously obtain the coordinat...Main cable line shape measurement and parameter identification are a critical task in the construction monitoring and service maintenance of suspension bridges.3D LiDAR scanning can simultaneously obtain the coordinates of multiple points on the target,offering high accuracy and efficiency.As a result,it is expected to be used in applications requiring rapid,large-scale measurements,such as main cable line shape measurement for suspension bridges.However,due to the large span and tall main towers of suspension bridges,the LiDAR field of view often encounters obstructions,making it difficult to obtain high-quality point clouds for the entire bridge.The collected point clouds are typically unevenly distributed and of poor quality.Therefore,LiDAR is used to monitor the local cable line shape.This paper proposes an innovative non-uniform sampling method that adjusts the sampling density based on the main cable’s rate of change.Additionally,the Random Sample Consensus(RANSAC)algorithm,the ordinary least squares,and center-of-mass calibration are applied to identify and optimize the geometric parameters of the cross-section point cloud of the main cable.Given the strong design prior information available during suspension bridge construction,Bayesian theory is applied to predict and adjust the global line shape of the main cable.The study shows that using LiDAR for cable point cloud measurement enables rapid acquisition of high-precision point cloud data,significantly enhancing data collection efficiency.The method proposed in this paper offers advantages such as highly automated,low risk,low cost,and sustainability,making it suitable for green monitoring throughout the entire main cable construction process.展开更多
基金supported by the U.S.National Science Foundation CAREER grant(CHE-1455353)the Oregon State University(OSU) Research Equipment Reserve Fund(Spring 2014)to C.Fang(USTC9603)the Wei Family Private Foundation in supporting C.Chen(USTC 0903) during his graduate studies at OSU Chemistry
文摘Resonance enhancement has been increasingly employed in the emergent felntosecond stimu- lated Raman spectroscopy （FSRS） to selectively monitor molecular structure and dynamics with improved spectral and temporal resolutions and signal-to-noise ratios. Such joint eflforts by the technique- and application-oriented scientists and engineers have laid the foundation for exploiting the tunable FSRS methodology to investigate a great variety of photosensitive systems and elucidate the underlying functional mechanisms on molecular time scales. Dur- ing spectral analysis, peak line shapes remain a major concern with an intricate dependence on resonance conditions. Here, we present a comprehensive study of line shapes by tuning the Rarnan pump wavelength from red to blue side of the ground-state absorption band of the fluorescent dye rhodarnine 6G in solution. Distinct line shape patterns in Stokes and anti-Stokes FSRS as well as from the low to high-frequency modes highlight the competition between multiple third-order and higher-order nonlinear pathways, governed by difl^rent res- onance conditions achieved by Raman pump and probe pulses. In particular, the resonance condition of probe wavelength is revealed to play an important role in generating circular line shape changes through oppositely phased dispersion via hot luminescence （HL） pathways. Meanwhile, on-resonance conditions of the Rarnan pump could promote excited-state vibrational modes which are broadened and red-shifted from the coincident ground-state vibrational modes, posing challenges for spectral analysis. Certain strategies in tuning the Raman pump and probe to characteristic regions across an electronic transition band are discussed to improve the FSRS usability and versatility as a powerful structural dynamics toolset to advance chemical, physical, materials, and biological sciences.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11374041 and 11404030the Fund of State Key Laboratory of Information Photonics and Optical Communications of Beijing University of Posts and Telecommunications of China
文摘We numerically investigate a coupled-resonator structure consisting of a stub resonator and a nanodisk resonator using a two-dimensional finite element method. Simulation results show that plasmon-induced transparency （PIT） occurs in the transmission spectra, and the sharp asymmetric Fano lines increase the sensitivity to 1.4 ×10^3 nm/RIU. We also analyze the properties of the structure with different radii of the nanodisk and the length of the tooth cavity. Moreover, we find that the PIP only happens when the staggered system is around a fixed location with different separate distances, which is not similar to the previous researches. Our model may be important to photonic-integrated circuits and the sensitivity in sensors.
基金funding from the Swedish Research Council(Nos.2020-04935 and 2021-05072)as well as computational resources provided by the National Academic Infrastructure for Supercomputing in Sweden at NSC,PDCC3SE partially funded by the Swedish Research Council through grant agreement No.2022-06725+1 种基金as well as the Berzelius resource provided by the Knut and Alice Wallenberg Foundation at NSC.Parts of the computations were performed on resources provided by UNINETT Sigma2-the National Infrastructure for High-Performance Computing and Data Storage in Norway.C.L.acknowledges the support provided by the Research Council of Norway and the University of Oslo through the research project QuTe(no.325573,FriPro ToppForsk-program)funding from the Swedish Strategic Research Foundation through a Future Research Leader program(FFL21-0129).
文摘Color centers play key roles in,e.g.,solid state lighting and quantum information technology.Here,we describe an approach for predicting the optical line shapes of such emitters based on direct sampling of the underlying autocorrelation functions through molecular dynamics simulations(MD-ACF).The energy landscapes are represented by a machine-learned potential that describes both the ground and excited state landscapes through a single model,guaranteeing size-consistent predictions.We apply this methodology to the(V_(Si)V_(C))_(kk)^(0)divacancy defect in 4H-SiC and demonstrate that at low temperatures,the present MD-ACF approach reproduces results from the traditional generating function approach.Unlike the latter,it is,however,also applicable at high temperatures as it avoids harmonic and parallel-mode approximations and can be applied to study non-crystalline materials.The MD-ACF methodology thus promises to substantially widen the range of computational predictions of the optical properties of color centers and related defects.
基金support of the Joint Centre for Extreme Photonics.Funding:This work is supported by the start-up grant of ShanghaiTech University,Double First-Class Initiative Fund of ShanghaiTech University,Shanghai Rising-Star Program(22QA1406200)National Natural Science Foundation of China(12274297,92250303)+7 种基金Shanghai Science and Technology Program(21511105000)NSERC Discovery Grant program(RGPIN-327147-2012)by the U.S.Army Research Office through Award W911NF-14-1-0383Part of this research used Beamline 03U of the Shanghai Synchrotron Radiation Facilitysupported by the ME2 project under contract no.11227902the National Natural Science Foundation of China.Y.F.and C.J.are supported by the National Natural Science Foundation of China(12274230,91950102,and 11834004)Funding of NJUST(TSXK2022D005)H.X.is supported by the National Natural Science Foundation of China(12074063 and 12264003)。
文摘Ultrafast extreme ultraviolet (XUV) transient absorption spectroscopy measures the time- and frequencydependent light losses after light–matter interactions. In the linear region, the matter response to an XUV light field is usually determined by the complex refractive index ̃n. The absorption signal is directly related to the imaginary part of ̃n, namely, the absorption index. The real part of ̃n refers to the real refractive index, which describes the chromatic dispersion of an optical material. However, the real refractive index information is usually not available in conventional absorption experiments. Here, we investigate the refractive index line shape in ultrafast XUV transient absorption spectroscopy by using a scheme that the XUV pulse traverses the target gas jet off-center. The jet has a density gradient in the direction perpendicular to the gas injection direction, which induces deflection on the XUV radiation. Our experimental and theoretical results show that the shape of the frequency-dependent XUV deflection spectra reproduces the refractive index line profile. A typical dispersive refractive index line shape is measured for a single-peak absorption;an additional shoulder structure appears for a doublet absorption.Moreover, the refractive index line shape is controlled by introducing a later-arrived near-infrared pulse to modify the phase of the XUV free induction decay, resulting in different XUV deflection spectra. The results promote our understanding of matter-induced absorption and deflection in ultrafast XUV spectroscopy.
文摘The line shapes to observe ηc in charmonium transitions, i.e., ψ（2S）, J/ψ→γηc, are investigated. The ηc line shapes in exclusive decays or by observing the inclusive photon spectrum are given. The sensitivities to measure the ηc resonance parameters are also evaluated. With more than two thousand ηc events observed, the precision of the ηc decay width measurement will be improved by better than 3%. However, the uncertainties associated with the ηc modified line shapes will dominate the systematic errors and this will prohibit precision mass and width measurements.
基金Project supported by the National Natural Science Foundation of China (Grant No. 12274230)the Funding of Nanjing University of Science and Technology (Grant No. TSXK2022D005)。
文摘The attosecond extreme ultraviolet(XUV) pulse pump and femtosecond infrared(IR) pulse probe scheme is commonly used to study the dynamics and attosecond transient absorption(ATA) spectra of microscopic systems. In a recent report [Proc. Natl. Acad. Sci. USA 121 e2307836121(2024)], we showed that shaped XUV pulses with spectral minima can significantly alter the absorption line shape of helium's 2s2p doubly excited state within a few tens of attoseconds.However, it remains unclear if similar effects could be observed in a singly excited state. In this study, we use shaped XUV pulses to excite helium's 2p singly excited state and couple the 2p and 3d states with a delayed IR pulse. Comparing these results with those from Gaussian XUV pulses, we find that the ATA spectra for the shaped XUV pulses exhibit more pronounced changes with delay, while the changes for the Gaussian pulses are gradual. We also explain these differences through population changes and analytical models. Our findings show that shaped XUV pulses can regulate the dynamics and absorption spectra of a singly excited state.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11174280,60990323,and 60990320)the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No.YYYJ-1123)
文摘We present the design and the experimental demonstration of an invisible cloak with irregular shape by using tensor transmission line（TL） metamaterials. The fabricated cloak consists of tensor TL unit cells exhibiting anisotropic effective material parameters, while the background medium consists of isotropic TL unit cells. The simulated and the measured field patterns around the cloak show a fairly good agreement, both demonstrate that the fabricated cloak can shield the cloaked interior area from electromagnetic fields without perturbing the external fields. The scattering of the cloaked perfect electric conductor（PEC） is minimized. Furthermore, the nonresonant property of the TL structure results in a relatively broad bandwidth of the realized cloak, which is clearly observed in our experiment.
基金Project supported by the National Natural Science Foundation of China (Grant No. 60971038)the Fundamental Research Funds for the Central Universities (Grant No. ZYGX2009Z003)
文摘The study on a miniaturized, low-voltage, wide-bandwidth, high-efficiency modified V-shaped microstrip meander-line slow-wave structure is presented. This structure is evolved from the original U-shaped microstrip meander-line slow-wave structure, combining the advantages of a traditional microstrip and a rectangular helix. In this paper, simulations of the electromagnetic characteristics and the beam-wave interaction of this structure are carried out. Our study shows that when the design voltage and the current of a sheet electron beam are set to be 4700 V and 100 mA, respectively, this miniature millimeter-wave power amplifier is capable of delivering 160-W output power with a corresponding gain of 37.3 dB and a maximum interaction efficiency of 34% at 97 GHz.
基金supported by the National Natural Science Foundation of China(Grant No.11074248)
文摘The influences of different buffer gas, neon and helium, on 199^Hg^＋ clock transition are compared in trapped 199^Hg^＋ linear trap. By the technique of time domain＇s Ramsey separated oscillatory fields, the buffer gas pressure frequency shifts of 199^Hg^＋ clock transition are measured to be （df/dPNe）（1/f） = 1.8 × 10^-8 Torr^-1 for neon and （df/dPHe） （1/f） = 9.1 × 10^-8 Torr^-1 for helium. Meanwhile, the line-width of 199^Hg^＋ clock transition spectrum with the buffer gas neon is narrower than that with helium at the same pressure. These experimental results show that neon is a more suitable buffer gas than helium in 199^Hg^＋ ions microwave frequency standards because of the 199^Hg^＋ clock transition is less sensitive to neon variations and the better cooling effect of neon. The optimum operating pressure for neon is found to be about 1.0 × 10^-5 Torr in our linear ion trap system.
基金Project supported by the National Basic Research Program of China (Grant No. 2012CB921603)the National High Technology Research and Development of China (Grant No. 2009AA01Z319)+3 种基金the National Natural Science Foundation of China (Grant Nos.61008012,10934004,60978018,60978001,60808009, and 11074154)the Science Fund for Creative Research Groups of the National Natural Science Foundation of China (Grant No. 60821004)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20101401120004)the National Natural Science Foundation of Shanxi Province,China (Grant No. 2009011059-2)
文摘We propose a technique to precisely measure the line width of the photoassociation spectra of the excited cesium molecule by using a frequency shifter to generate two laser beams with a precise frequency difference. A series of photoassociation （PA） spectra are recorded with two laser beam induced molecular lines, whose peak separation serves as an accurate frequency ruler to measure the line width of the PA spectra. The full width half maximum line width was studied as a function of PA laser intensity. The extrapolated value at zero laser intensity is （34.8± 0.22） MHz. By analyzing other broadening mechanisms, a value of （32.02 ± 0.70） MHz was deduced. It is shown that this scheme is inexpensive, simple, robust, and is promising for applications in a variety of other atomic species.
基金the National High Magnetic Field Laboratory(NHMFL,USA)through NSF DMR-1644779 and the State of Florida.
文摘NMR spectra acquired with experiments using frequency-sweeps such as the wide-band uniform-rate smooth truncation(WURST)spin-echo and Carr-Purcell-Meiboom-Gill(CPMG)sequences cannot be absorptively phased by using only conventional zerothand first-order phase correction.Implementation of phase correction up to the secondorder is described for obtaining absorptive spectra,which have more desirable line shapes and noise properties than magnitude spectra.The relationship of the second-order phase to the parameters of frequency sweeps is derived.The second-order phasing in the frequency-domain is equivalent to a point spread in the time-domain signal.The application of second-order phase correction is demonstrated with a wideline 35Cl CPMG spikelet spectrum.
基金funded by the 2024 STCSM Shanghai Natural Science Grants General Project"Online Intelligent Perception and Warning of Large span Structural Vortex Vibration Based on Structural Health Monitoring"and the Science and Technology Project"Research on Intelligent Monitoring System Scheme for Large span Bridges in Mountainous Areas"of PowerChina Road Bridge Group Co.,Ltd.
文摘Main cable line shape measurement and parameter identification are a critical task in the construction monitoring and service maintenance of suspension bridges.3D LiDAR scanning can simultaneously obtain the coordinates of multiple points on the target,offering high accuracy and efficiency.As a result,it is expected to be used in applications requiring rapid,large-scale measurements,such as main cable line shape measurement for suspension bridges.However,due to the large span and tall main towers of suspension bridges,the LiDAR field of view often encounters obstructions,making it difficult to obtain high-quality point clouds for the entire bridge.The collected point clouds are typically unevenly distributed and of poor quality.Therefore,LiDAR is used to monitor the local cable line shape.This paper proposes an innovative non-uniform sampling method that adjusts the sampling density based on the main cable’s rate of change.Additionally,the Random Sample Consensus(RANSAC)algorithm,the ordinary least squares,and center-of-mass calibration are applied to identify and optimize the geometric parameters of the cross-section point cloud of the main cable.Given the strong design prior information available during suspension bridge construction,Bayesian theory is applied to predict and adjust the global line shape of the main cable.The study shows that using LiDAR for cable point cloud measurement enables rapid acquisition of high-precision point cloud data,significantly enhancing data collection efficiency.The method proposed in this paper offers advantages such as highly automated,low risk,low cost,and sustainability,making it suitable for green monitoring throughout the entire main cable construction process.
