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Time-domain mode retrieval of ultrafast dynamics in dielectric metasurfaces with quasi-BIC resonances 认领 引用
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作者 Hao Wu Andrey E.Miroshnichenko 《Advanced Photonics Nexus》 CSCD 2026年第5期236-243,共8页
Dielectric metasurfaces and other resonant nanophotonic systems have transformed light–matter interactions by providing exact control over electromagnetic fields.Despite the fact that these systems frequently span mu... Dielectric metasurfaces and other resonant nanophotonic systems have transformed light–matter interactions by providing exact control over electromagnetic fields.Despite the fact that these systems frequently span multiple coupling regimes and may thus exhibit rich intrinsic temporal dynamics,characterizing them has primarily relied on steady-state frequency-domain analysis.To close this gap,we present a thorough time-domain mode-retrieval framework.The decoupling of resonant modes from the background continuum is made possible by systematically extracting the complex resonant poles of a nanophotonic system directly from its transient response using the vector fitting technique and the Prony method.Specifically,we investigate resonances supported by a silicon metasurface that are quasi-bound states in the continuum(quasi-BICs).This method effectively separates radiative quasi-BIC modes and identifies their fundamental properties,such as the Q-factors.In addition,our approach uncovers a clear temporal beating behavior associated with transient mode interference that is not visible in steady-state spectral measurements.Lastly,this method is expanded to the nonlinear regime to see the third-harmonic generation signal’s temporal evolution.Our results open up possibilities for ultrafast all-optical devices with customized temporal dynamics by establishing a potent semi-analytical tool for time-resolved investigations of ultrafast dynamics in resonant nanophotonic systems. 展开更多
关键词 temporal dynamics quasi-bound states in the continuum dielectric metasurfaces time-domain mode retrieval
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A Time-Domain Irregular Wave Model with Different Random Numbers for FOWT Support Structures 认领 引用
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作者 Shen-Haw Ju Yi-Chen Huang 《Computer Modeling in Engineering & Sciences》 SCIE EI 2025年第8期1631-1654,共24页
This study focuses on determining the second-order irregular wave loads in the time domain without using the Inverse Fast Fourier Transform(IFFT).Considering the substantial displacement effects that Floating Offshore... This study focuses on determining the second-order irregular wave loads in the time domain without using the Inverse Fast Fourier Transform(IFFT).Considering the substantial displacement effects that Floating Offshore Wind Turbine(FOWT)support structures undergo when subjected to wave loads,the time-domain wave method is more suitable,while the frequency-domain method requiring IFFT cannot be used for moving bodies.Nonetheless,the computational challenges posed by the considerable computer time requirements of the time-domain wave method remain a significant obstacle.Thus,the paper incorporates various numerical schemes,including parallel computing and extrapolation of wave forces during specific time steps to improve overall efficiency.Despite the effectiveness of these schemes,the computational difficulties associated with the time-domain wave method persist.This study then proposes an innovative approach utilizing different randomnumbers in distinct segments,significantly reducing the computation of second-order wave loads.This random number interpolation ensures a smooth curve transition between two segments,emphasizingminimizing errors near the end of the first segment.Numerical analyses demonstrate substantial decreases in total computer time for FOWT structural analyses while maintaining consistent steel design results.The proposed method is uncomplicated,requiring only a simple subprogram modification in a conventional wave load computer program. 展开更多
关键词 Fast fourier transform finite element method floating offshore wind turbine irregular wave parallel computing time-domain wave loads
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Terahertz imaging technology:progress and applications 认领 引用 被引量：1
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作者 Yuyuan Tian Xiaoyin Chen +13 位作者 Zhuocheng Zhang Qianze Yan Yiming Liu Chengliang Deng Min Wan Jiang Li Xiaoqiuyan Zhang Lu Rong Elizaveta Tsiplakova Nikolay Petrov Xinke Wang Liguo Zhu Min Hu Yan Zhang 《Opto-Electronic Technology》 2026年第1期1-71,I0001,I0002,共71页
Terahertz imaging,operating within the 0.1–10 THz frequency range,leverages unique properties such as non-ionizing radiation,sensitivity to polar molecules,and material-specific spectral fingerprints.This review comp... Terahertz imaging,operating within the 0.1–10 THz frequency range,leverages unique properties such as non-ionizing radiation,sensitivity to polar molecules,and material-specific spectral fingerprints.This review comprehensively surveys major terahertz imaging modalities,highlighting significant progress and applications.Key methodologies,including continuous-wave holography,lensless ptychography,and computed tomography,provide quantitative phase contrast and three-dimensional structural information.Notably,terahertz pulse time-domain holography leverages the broadband nature of pulsed sources to achieve depth-resolved imaging through time-gated analysis.The development of focal-plane and single-pixel imaging addresses challenges related to detector availability,enabling high-speed and cost-effective systems.A major breakthrough is observed in near-field imaging,which surpasses the diffraction limit to achieve nanoscale resolution for probing materials,biomolecules,and plasmonic phenomena.While challenges in signal-to-noise ratio,hardware integration,and imaging speed persist,ongoing innovations in laser sources,algorithms,and system design are driving adoption in security,biomedicine,and industrial inspection. 展开更多
关键词 terahertz imaging continuous-wave focal-plane time-domain holography single-pixel near-field
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Nonlinear Seismic Response of Tunnels in Longitudinally Inhomogeneous Strata Subjected to Obliquely Incident SV Waves 认领 引用
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作者 Xiaole Jiang Jingqi Huang +2 位作者 Xu Zhao Wenlong Ouyang Xianghui Zhao 《Computer Modeling in Engineering & Sciences》 SCIE EI 2026年第3期388-415,共28页
To address the complex seismic response of long tunnels longitudinally crossing heterogeneous geological formations,this study proposes a three-dimensional SV-wave oblique-incidence input method that accounts for the ... To address the complex seismic response of long tunnels longitudinally crossing heterogeneous geological formations,this study proposes a three-dimensional SV-wave oblique-incidence input method that accounts for the initial disturbance of the wave field induced by geological heterogeneity.The method transforms equivalent twodimensional free-field responses into equivalent nodal forces applied at the boundaries of a 3D numerical model.A longitudinally heterogeneous“hard-soft-hard”site and tunnel system is established,in which the surrounding rock is modeled using the Mohr-Coulomb constitutive law,while the concrete lining is described by the concrete damaged plasticity model.The deformation patterns and failure mechanisms of the site-tunnel system under SV-wave excitation are systematically investigated.The results indicate that seismic damage under SV-wave loading is mainly concentrated in the soft-rock region.Failure of the soft surrounding rock induces pronounced sliding of the overlying hard rock,and the tunnel suffers severe damage due to the combined effects of soft-rock failure and strong ground shaking.Parametric analyses further show that smaller impedance ratios,larger soft-rock widths,and larger incidence angles significantly intensify the seismic response of the tunnel.The findings of this study provide valuable insights for the seismic design of tunnels crossing longitudinally heterogeneous geological formations. 展开更多
关键词 Inhomogeneous geology SV waves tunnel earthquake time-domain wave propagation approach
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DRL-enabled secure uplink transmission for MIMO-OFDM IoT systems against intelligent eavesdroppers 认领 引用
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作者 Yingzhen Wu Yan Huo +3 位作者 Xin Fan Qinghe Gao Jian Mao Tao Jing 《Digital Communications and Networks》 SCIE EI CSCD 2026年第3期428-440,共13页
Physical layer security has emerged as a promising approach to counter eavesdropping threats in the Internet of Things(IoT).With the advancement of technology,eavesdroppers(Eves)are increasingly sophisticated,exacerba... Physical layer security has emerged as a promising approach to counter eavesdropping threats in the Internet of Things(IoT).With the advancement of technology,eavesdroppers(Eves)are increasingly sophisticated,exacerbating the difficulties in ensuring the security of uplink transmissions.In situations where transmitters are unable to deter Eves from approaching at close range,these intelligent Eves can attain substantial channel gains,thereby posing significant security threats.To address these challenges,we first propose a time-domain artificial noise(AN)scheme to eliminate interference at the legitimate receiver in Multiple-Input Multiple-Output Orthogonal Frequency Division Multiplexing(MIMO-OFDM)systems.Then,we model the adversarial interaction between legitimate transceivers and intelligent Eves as a game-theoretic problem.To solve the dynamic game problem,we introduce a deep deterministic policy gradient(DDPG)-based framework,where an optimal beamforming fractional programming algorithm(OBFP)and a lower-complexity zero-forcing beamforming difference of convex algorithm(ZFDC)are designed to ascertain the most effective strategy for legitimate transceivers.Simulation results validate the effectiveness of our proposed algorithms and highlight the critical role of time-domain AN in combating intelligent eavesdropping. 展开更多
关键词 Physical layer security IoT Intelligent eavesdroppers Time-domain artificial noise Convex optimization Deep reinforcement learning
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Investigation of copper sulfate pentahydrate dehydration by terahertz time-domain spectroscopy 认领 引用 被引量：8
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作者 Yuan-Yuan Ma Hao-Chong Huang +3 位作者 Si-Bo Hao Wei-Chong Tang Zhi-Yuan Zheng Zi-Li Zhang 《Chinese Physics B》 SCIE EI CAS CSCD 2019年第6期110-113,共4页
Copper sulfate pentahydrate is investigated by terahertz time-domain spectroscopy. It is shown that the terahertz absorption coefficients are correlated with the particle size of the samples, as well as the heating ra... Copper sulfate pentahydrate is investigated by terahertz time-domain spectroscopy. It is shown that the terahertz absorption coefficients are correlated with the particle size of the samples, as well as the heating rates of the ambient temperature. Furthermore, the water molecules of copper sulfate pentahydrate can be quantitatively characterized due to the high sensitivity of the terahertz wave to water molecules. Based on such results, the status of water incorporated in mineral opal is also characterized using terahertz time-domain spectroscopy. It indicates that terahertz technology can be considered as an efficient method to detect the dehydration of minerals. 展开更多
关键词 copper sulfate pentahydrate water status terahertz time-domain spectroscopy
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PC-based artif icial neural network inversion for airborne time-domain electromagnetic data 认领 引用 被引量：12
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作者 朱凯光 马铭遥 +4 位作者 车宏伟 杨二伟 嵇艳鞠 于生宝 林君 《Applied Geophysics》 SCIE CSCD 2012年第1期1-8,114,共8页
Traditionally, airborne time-domain electromagnetic （ATEM） data are inverted to derive the earth model by iteration. However, the data are often highly correlated among channels and consequently cause ill-posed and ... Traditionally, airborne time-domain electromagnetic （ATEM） data are inverted to derive the earth model by iteration. However, the data are often highly correlated among channels and consequently cause ill-posed and over-determined problems in the inversion. The correlation complicates the mapping relation between the ATEM data and the earth parameters and thus increases the inversion complexity. To obviate this, we adopt principal component analysis to transform ATEM data into orthogonal principal components （PCs） to reduce the correlations and the data dimensionality and simultaneously suppress the unrelated noise. In this paper, we use an artificial neural network （ANN） to approach the PCs mapping relation with the earth model parameters, avoiding the calculation of Jacobian derivatives. The PC-based ANN algorithm is applied to synthetic data for layered models compared with data-based ANN for airborne time-domain electromagnetic inversion. The results demonstrate the PC-based ANN advantages of simpler network structure, less training steps, and better inversion results over data-based ANN, especially for contaminated data. Furthermore, the PC-based ANN algorithm effectiveness is examined by the inversion of the pseudo 2D model and comparison with data-based ANN and Zhody＇s methods. The results indicate that PC-based ANN inversion can achieve a better agreement with the true model and also proved that PC-based ANN is feasible to invert large ATEM datasets. 展开更多
关键词 Principal component analysis artificial neural network airborne time-domain electromagnetics inversion conductivity
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Brillouin optical time-domain analysis for geotechnical monitoring 认领 引用 被引量：19
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作者 L.Zeni L.Picarelli +6 位作者 B.Avolio A.Coscetta R.Papa G.Zeni C.Di Maio R.Vassallo A.Minardo 《Journal of Rock Mechanics and Geotechnical Engineering》 CSCD 2015年第4期458-462,共5页
In this paper,we show some recent experimental applications of Brillouin optical time-domain analysis(BOTDA)based sensors for geotechnical monitoring.In particular,how these sensors can be applied to detecting early m... In this paper,we show some recent experimental applications of Brillouin optical time-domain analysis(BOTDA)based sensors for geotechnical monitoring.In particular,how these sensors can be applied to detecting early movements of soil slopes by the direct embedding of suitable fiber cables in the ground is presented.Furthermore,the same technology can be used to realize innovative inclinometers,as well as smart foundation anchors. 展开更多
关键词 Brillouin optical time-domain analysis(BOTDA) Tunnel engineering Deformation Distributed monitoring Health diagnosis
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Inversion of time-domain airborne EM data with IP effect based on Pearson correlation constraints 认领 引用 被引量：4
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作者 Man Kai-Feng Yin Chang-Chun +4 位作者 Liu Yun-He Ren Xiu-Yan Sun Si-Yuan Miao Jia-Jia Xiong Bin 《Applied Geophysics》 SCIE CSCD 2020年第4期589-600,共12页
Due to the induced polarization(IP)eff ect,the sign reversal often occurs in timedomain airborne electromagnetic(AEM)data.The inversions that do not consider IP eff ect cannot recover the true umderground electrical s... Due to the induced polarization(IP)eff ect,the sign reversal often occurs in timedomain airborne electromagnetic(AEM)data.The inversions that do not consider IP eff ect cannot recover the true umderground electrical structures.In view of the fact that there are many parameters of airborne induced polarization data in time domain,and the sensitivity diff erence between parameters is large,which brings challenges to the stability and accuracy of the inversion.In this paper,we propose an inversion mehtod for time-domain AEM data with IP effect based on the Pearson correlation constraints.This method uses the Pearson correlation coeffi cient in statistics to characterize the correlation between the resistivity and the chargeability and constructs the Pearson correlation constraints for inverting the objective function to reduce the non uniqueness of inversion.To verify the eff ectiveness of this method,we perform both Occam’s inversion and Pearson correlation constrained inversion on the synthetic data.The experiments show that the Pearson correlation constrained inverison is more accurate and stable than the Occam’s inversion.Finally,we carried out the inversion to a survey dataset with and without IP eff ect.The results show that the data misfit and the continuity of the inverted section are greatly improved when the IP eff ect is considered. 展开更多
关键词 Time-domain AEM induced polarization effect forward modeling inversion Pearson correlation constraints
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Three-dimensional arbitrarily anisotropic modeling for time-domain airborne electromagnetic surveys 认领 引用 被引量：6
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作者 黄威 贲放 +5 位作者 殷长春 孟庆敏 李文杰 廖桂香 吴珊 西永在 《Applied Geophysics》 SCIE CSCD 2017年第3期431-440,462,共10页
Electrically anisotropic strata are abundant in nature, so their study can help our data interpretation and our understanding of the processes of geodynamics. However, current data processing generally assumes isotrop... Electrically anisotropic strata are abundant in nature, so their study can help our data interpretation and our understanding of the processes of geodynamics. However, current data processing generally assumes isotropic conditions when surveying anisotropic structures, which may cause discrepancies between reality and electromagnetic data interpretation. Moreover, the anisotropic interpretation of the time-domain airborne electromagnetic （TDAEM） method is still confined to one dimensional （1D） cases, and the corresponding three-dimensional （3D） numerical simulations are still in development. In this study, we expanded the 3D TDAEM modeling of arbitrarily anisotropic media. First, through coordinate rotation of isotropic conductivity, we obtained the conductivity tensor of an arbitrary anisotropic rock. Next, we incorporated this into Maxwell＇s equations, using a regular hexahedral grid of vector finite elements to subdivide the solution area. A direct solver software package provided the solution for the sparse linear equations that resulted. Analytical solutions were used to verify the accuracy and feasibility of the algorithm. The proven model was then applied to analyze the effects of arbitrary anisotropy in 3D TDAEM via the distribution of responses and amplitude changes, which revealed that different anisotropy situations strongly affected the responses of TDAEM. 展开更多
关键词 Three-dimensional time-domain airborne electromagnetic arbitrary anisotropy vector finite element
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Time-domain dynamic constitutive model suitable for mucky soil site seismic response 认领 引用 被引量：6
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作者 Dong Qing Chen Su +2 位作者 Jin Liguo Zhou Zhenghua Li Xiaojun 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2024年第1期1-13,共13页
Soil nonlinear behavior displays noticeable effects on the site seismic response.This study proposes a new functional expression of the skeleton curve to replace the hyperbolic skeleton curve.By integrating shear modu... Soil nonlinear behavior displays noticeable effects on the site seismic response.This study proposes a new functional expression of the skeleton curve to replace the hyperbolic skeleton curve.By integrating shear modulus and combining the dynamic skeleton curve and the damping degradation coefficient,the constitutive equation of the logarithmic dynamic skeleton can be obtained,which considers the damping effect in a soil dynamics problem.Based on the finite difference method and the multi-transmitting boundary condition,a 1D site seismic response analysis program called Soilresp1D has been developed herein and used to analyze the time-domain seismic response in three types of sites.At the same time,this study also provides numerical simulation results based on the hyperbolic constitutive model and the equivalent linear method.The results verify the rationality of the new soil dynamic constitutive model.It can analyze the mucky soil site nonlinear seismic response,reflecting the deformation characteristics and damping effect of the silty soil.The hysteresis loop area is more extensive,and the residual strain is evident. 展开更多
关键词 seismic response time-domain dynamic constitutive model logarithmic dynamic skeleton dampening effect mucky soil
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Phase-Sensitive Optical Time-Domain Reflectometer Based on a 120°-Phase-Difference Michelson Interferometer 认领 引用 被引量：4
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作者 曹玉龙 杨飞 +3 位作者 徐丹 叶青 蔡海文 方祖捷 《Chinese Physics Letters》 SCIE EI CAS CSCD 2016年第5期22-25,共4页
A phase-sensitive optical time domain reflectometer （φ-OTDR） based on a 120°-phase-difference Michelson in- terferometer is proposed. The Michelson interferometer with arm difference of 4m is used to test the ... A phase-sensitive optical time domain reflectometer （φ-OTDR） based on a 120°-phase-difference Michelson in- terferometer is proposed. The Michelson interferometer with arm difference of 4m is used to test the phase difference between the Rayleigh scattering from two sections of the fiber. A new demodulation method called the inverse transmission matrix demodulation scheme is utilized to demodulate the distributed phase from the backward scattering along the long fiber, The experimental results show that the 120°-phase-difference inter- ferometer φ-OTDR can detect the phase along the 3km fiber, and the acoustic signal within the whole human hearing range of 20 Hz-20 kHz is reproduced accurately and quickly. 展开更多
关键词 of is Phase-Difference Michelson Interferometer Phase-Sensitive Optical Time-Domain Reflectometer Based on a 120 on into kHz EDFA with be that
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Comparison of the time-domain electromagnetic field from an infinitesimal point charge and dipole source 认领 引用 被引量：8
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作者 周楠楠 薛国强 王贺元 《Applied Geophysics》 SCIE CSCD 2013年第3期349-356,359,共8页
An electromagnetic field is generated through the accelerating movement of two equal but opposite charges of a single dipole. An electromagnetic field can also be generated by a time-varying infinitesimal point charge... An electromagnetic field is generated through the accelerating movement of two equal but opposite charges of a single dipole. An electromagnetic field can also be generated by a time-varying infinitesimal point charge. In this study, a comparison between the electromagnetic fields of an infinitesimal point charge and a dipole has been presented. First, the time-domain potential function of a point source in a 3D conductive medium is derived. Then the electric and magnetic fields in a 3D homogeneous lossless space are derived via the relation between the potential and field. The field differences between the infinitesimal point charge and the dipole in the step-off time, far-source, and near-source zones are analyzed, and the accuracy of the solutions from these sources is investigated. It is also shown that the field of the infinitesimal point charge in the near-source zone is different from that of the dipole, whereas the far-source zone fields of these two sources are identical. The comparison of real and simulated data shows that the infinitesimal point charge represents the real source better than the divole source. 展开更多
关键词 Infinitesimal point charge dipole source time-domain electromagnetic response near-source zone.
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Solution and Analysis of Chatter Stability for End Milling in the Time-domain 认领 引用 被引量：50
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作者 李忠群 刘强 《Chinese Journal of Aeronautics》 SCIE EI CAS 2008年第2期169-178,共10页
In this paper, the instantaneous undeformed chip thickness is modeled to include the dynamic modulation caused by the tool vibration while the dynamic regenerative effects are taken into account. The numerical method ... In this paper, the instantaneous undeformed chip thickness is modeled to include the dynamic modulation caused by the tool vibration while the dynamic regenerative effects are taken into account. The numerical method is used to solve the differential equations goveming the dynamics of the milling system. Several chatter detection criteria are applied synthetically to the simulated signals and the stability diagram is obtained in time-domain. The simulation results in time-domain show a good agreement with the analytical prediction, which is validated by the cutting experiments. By simulating the chatter stability lobes in the time-domain and analyzing the influences of different spindle speeds on the vibration amplitudes of the tool under a Fixed chip-load condition, conclusions could be drawn as follows： In rough milling, higher machining efficiency can be achieved by selecting a spindle speed corresponding to the axial depth of cut in accordance with the simulated chatter stability lobes, and in Fmish milling, lower surface roughness can be achieved by selecting a spindle speed well beyond the resonant frequency of machining system. 展开更多
关键词 high-speed milling chatter stability lobe dynamic cutting force time-domain simulation cutting parameter optimization
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Perfect plane-wave source for a high-order symplectic finite-difference time-domain scheme 认领 引用 被引量：5
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作者 王辉 黄志祥 +1 位作者 吴先良 任信钢 《Chinese Physics B》 SCIE EI CAS CSCD 2011年第11期365-370,共6页
The method of splitting a plane-wave finite-difference time-domain （SP-FDTD） algorithm is presented for the initiation of plane-wave source in the total-field / scattered-field （TF/SF） formulation of high-order sy... The method of splitting a plane-wave finite-difference time-domain （SP-FDTD） algorithm is presented for the initiation of plane-wave source in the total-field / scattered-field （TF/SF） formulation of high-order symplectic finite- difference time-domain （SFDTD） scheme for the first time. By splitting the fields on one-dimensional grid and using the nature of numerical plane-wave in finite-difference time-domain （FDTD）, the identical dispersion relation can be obtained and proved between the one-dimensional and three-dimensional grids. An efficient plane-wave source is simulated on one-dimensional grid and a perfect match can be achieved for a plane-wave propagating at any angle forming an integer grid cell ratio. Numerical simulations show that the method is valid for SFDTD and the residual field in SF region is shrinked down to -300 dB. 展开更多
关键词 splitting plane-wave finite-difference time-domain high-order symplectic finite-differencetime-domain scheme plane-wave source
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Numerical modeling of the 2D time-domain transient electromagnetic secondary field of the line source of the current excitation 认领 引用 被引量：8
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作者 刘云 王绪本 王贇 《Applied Geophysics》 SCIE CSCD 2013年第2期134-144,235,共11页
To effectively minimize the electromagnetic field response in the total field solution, we propose a numerical modeling method for the two-dimensional （2D） time- domain transient electromagnetic secondary field of t... To effectively minimize the electromagnetic field response in the total field solution, we propose a numerical modeling method for the two-dimensional （2D） time- domain transient electromagnetic secondary field of the line source based on the DuFort- Frankel finite-difference method. In the proposed method, we included the treatment of the earth-air boundary conductivity, calculated the normalized partial derivative of the induced electromotive force （Emf）, and determined the forward time step. By extending upward the earth-air interface to the air grid nodes and the zero-value boundary conditions, not only we have a method that is more efficient but also simpler than the total field solution. We computed and analyzed the homogeneous half-space model and the fiat layered model with high precision--the maximum relative error is less than 0.01% between our method and the analytical method--and the solution speed is roughly three times faster than the total-field solution. Lastly, we used the model of a thin body embedded in a homogeneous half-space at different delay times to depict the downward and upward spreading characteristics of the induced eddy current, and the physical interaction processes between the electromagnetic field and the underground low-resistivity body. 展开更多
关键词 Time-domain transient electromagnetics secondary field DuFort-Frankel finite-difference method numerical modeling.
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Time-Domain Simulation for Coupled Motions of Three Barges Moored Side-by-Side in Floatover Operation 认领 引用 被引量：16
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作者 许鑫 杨建民 +1 位作者 李欣 徐亮瑜 《China Ocean Engineering》 SCIE EI CSCD 2015年第2期155-168,共14页
Simulating the coupled motions of multiple bodies in the time domain is a complex problem because of the strong hydrodynamic interactions and coupled effect of various mechanical connectors. In this study, we investig... Simulating the coupled motions of multiple bodies in the time domain is a complex problem because of the strong hydrodynamic interactions and coupled effect of various mechanical connectors. In this study, we investigate the hydrodynamic responses of three barges moored side-by-side in a floatover operation in the frequency and time domains. In the frequency domain, the damping lid method is adopted to improve the overestimated hydrodynamic coefficients calculated from conventional potential flow theory. A time-domain computing program based on potential flow theory and impulse theory is compiled for analyses that consider multibody hydrodynamic interactions and mechanical effects from lines and fenders. Correspondingly, an experiment is carried out for comparison with the numerical results. All statistics, time series, and power density spectra from decay and irregular wave tests are in a fairly good agreement. 展开更多
关键词 coupled motion time-domain simulation side-by-side floatover
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Far-infrared conductivity of CuS nanoparticles measured by terahertz time-domain spectroscopy 认领 引用 被引量：3
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作者 杨玉平 张振伟 +2 位作者 施宇蕾 冯帅 王文忠 《Chinese Physics B》 SCIE EI CAS 2010年第4期213-217,共5页
This paper reports that terahertz time-domain spectroscopy is used to measure the optical properties of CuS nanoparticles in composite samples. The complex conductivity of pure CuS nanoparticles is extracted by applyi... This paper reports that terahertz time-domain spectroscopy is used to measure the optical properties of CuS nanoparticles in composite samples. The complex conductivity of pure CuS nanoparticles is extracted by applying the Bruggeman effective medium theory. The experimental data are consistent with the Drude-Smith model of conductivity in the range of 0.2 1.5 THz. The results demonstrate that carriers become localized with a backscattering behaviour in small-size nanostructures. In addition, the time constant for the carrier scattering is obtained and is only 64.3 fs due to increased electron interaction with interfaces and grain boundaries. 展开更多
关键词 terahertz time-domain spectroscopy conductivity effective medium theory Drude-Smith model
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A Novel Quantitative Detection of Sleeve Grouting Compactness Based on Ultrasonic Time-Frequency Dual-Domain Analysis 认领 引用
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作者 Longqi Liao Jing Li +4 位作者 Yuhua Li Yuemin Wang Jinhua Li Liyuan Cao Chunxiang Li 《Structural Durability & Health Monitoring》 EI 2026年第1期138-160,共23页
Quantitative detection of sleeve grouting compactness is a technical challenge in civil engineering testing.This study explores a novel quantitative detection method based on ultrasonic time-frequency dual-domain anal... Quantitative detection of sleeve grouting compactness is a technical challenge in civil engineering testing.This study explores a novel quantitative detection method based on ultrasonic time-frequency dual-domain analysis.It establishes a mapping relationship between sleeve grouting compactness and characteristic parameters.First,this study made samples with gradient defects for two types of grouting sleeves,G18 and G20.These included four cases:2D,4D,6D defects(where D is the diameter of the grouting sleeve),and no-defect.Then,an ultrasonic input/output data acquisition system was established.Three-dimensional sound field distribution data were obtained through an orthogonal detection layout and pulse reflection principles.Finally,a novel quantification detection with a comprehensive defect index(DI)was established by comprehensively considering eight feature parameters,such as time-frequency domain Kurtosis factor(KU),Skewness factor(SK),Formfactor(FF),Crest factor(CF),Impulse factor(IF),Clearance factor(CLF),Wavelet packet energy entropy(WPEE),and Hilbert energy peak(HEP).Construct a DI index by quantifying the difference between defect signals and defect free signals in the time-frequency domain.Experimental results show that,under no-defect conditions,the values of feature parameters are significantly lower than those under defect conditions.Among these,the KU,FF,CF,WPEE and HEP exhibit strong correlations with grout sleeve compactness.The proposed DI index in both types of grout sleeves showed good universality with a linear fit goodness of 0.847–0.962.However,G20 the larger inner diameter and length of the sleeve result in a more complex medium effect during ultrasonic propagation,making its DI index more sensitive to defects than the G18 sleeve.Therefore,the presented method is effective for quantitative detection and analysis of the compactness of grouting sleeves. 展开更多
关键词 Sleeve grout compactness ultrasonic non-destructive testing time-domain dimensionless wavelet packet transform empirical mode decomposition Hilbert-Huang transform
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A 1D time-domain method for in-plane wave motions in a layered half-space 认领 引用 被引量：10
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作者 Jingbo Liu Yan Wang 《Acta Mechanica Sinica》 SCIE EI CAS 2007年第6期673-680,共8页
A 1D finite element method in time domain is developed in this paper and applied to calculate in-plane wave motions of free field exited by SV or P wave oblique incidence in an elastic layered half-space.First,the lay... A 1D finite element method in time domain is developed in this paper and applied to calculate in-plane wave motions of free field exited by SV or P wave oblique incidence in an elastic layered half-space.First,the layered half-space is discretized on the basis of the propagation characteristic of elastic wave according to the Snell law.Then,the finite element method with lumped mass and the central difference method are incorporated to establish 2D wave motion equations,which can be transformed into 1D equations by discretization principle and explicit finite element method.By solving the 1D equations,the displacements of nodes in any vertical line can be obtained,and the wave motions in layered half-space are finally determined based on the characteristic of traveling wave.Both the theoretical analysis and the numerical results demonstrate that the proposed method has high accuracy and good stability. 展开更多
关键词 In-plane wave Oblique incidence Time-domain method Snell law
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