The boundary value problem plays a crucial role in the analytical investigation of continuum dynamics. In this paper, an analytical method based on the Dirac operator to solve the nonlinear and non-homogeneous boundar...The boundary value problem plays a crucial role in the analytical investigation of continuum dynamics. In this paper, an analytical method based on the Dirac operator to solve the nonlinear and non-homogeneous boundary value problem of rectangular plates is proposed. The key concept behind this method is to transform the nonlinear or non-homogeneous part on the boundary into a lateral force within the governing function by the Dirac operator, which linearizes and homogenizes the original boundary, allowing one to employ the modal superposition method for obtaining solutions to reconstructive governing equations. Once projected into the modal space, the harmonic balance method(HBM) is utilized to solve coupled ordinary differential equations(ODEs)of truncated systems with nonlinearity. To validate the convergence and accuracy of the proposed Dirac method, the results of typical examples, involving nonlinearly restricted boundaries, moment excitation, and displacement excitation, are compared with those of the differential quadrature element method(DQEM). The results demonstrate that when dealing with nonlinear boundaries, the Dirac method exhibits more excellent accuracy and convergence compared with the DQEM. However, when facing displacement excitation, there exist some discrepancies between the proposed approach and simulations;nevertheless, the proposed method still accurately predicts resonant frequencies while being uniquely capable of handling nonuniform displacement excitations. Overall, this methodology offers a convenient way for addressing nonlinear and non-homogenous plate boundaries.展开更多
The influence of pavement vibration on tire adhesion is of great significance to the structure design of vehicle and pavement.The adhesion between tire and road is the key to studying vehicle dynamics,and the precise ...The influence of pavement vibration on tire adhesion is of great significance to the structure design of vehicle and pavement.The adhesion between tire and road is the key to studying vehicle dynamics,and the precise description of tire adhesion affects the accuracy of dynamic vehicle responses.However,in most models,only road roughness is considered,and the pavement vibration caused by vehicle-road interaction is ignored.In this paper,a vehicle is simplified as a spring-mass-damper oscillator,and the vehicle-pavement system is modeled as a vehicle moving along an Euler-Bernoulli beam with finite length on a nonlinear foundation.The road roughness is considered as a sine wave,and the shear stress is ignored on the pavement.According to the contact form between tire and road,the LuGre tire model is established to calculate the tire adhesion force.The Galerkin method is used to simplify the partial differential equations of beam vibration into finite ordinary differential equations.A product-to-sum formula and a Dirac delt function are used to deal with the nonlinear term caused by the nonlinear foundation,which realizes the fast and accurate calculation of super-high dimensional nonlinear ordinary differential equations.In addition,the dynamic responses between the coupled system and the traditional uncoupled system are compared with each other.The obtained results provide an important theoretical basis for research on the influence of vehicle-road coupled vibration on tire adhesion.展开更多
One of the technical bottlenecks of traditional laser-induced breakdown spectroscopy(LIBS) is the difficulty in quantitative detection caused by the matrix effect. To troubleshoot this problem,this paper investigated ...One of the technical bottlenecks of traditional laser-induced breakdown spectroscopy(LIBS) is the difficulty in quantitative detection caused by the matrix effect. To troubleshoot this problem,this paper investigated a combination of time-resolved LIBS and convolutional neural networks(CNNs) to improve K determination in soil. The time-resolved LIBS contained the information of both wavelength and time dimension. The spectra of wavelength dimension showed the characteristic emission lines of elements, and those of time dimension presented the plasma decay trend. The one-dimensional data of LIBS intensity from the emission line at 766.49 nm were extracted and correlated with the K concentration, showing a poor correlation of R_c^2?=?0.0967, which is caused by the matrix effect of heterogeneous soil. For the wavelength dimension, the two-dimensional data of traditional integrated LIBS were extracted and analyzed by an artificial neural network(ANN), showing R_v^2?=?0.6318 and the root mean square error of validation(RMSEV)?=?0.6234. For the time dimension, the two-dimensional data of time-decay LIBS were extracted and analyzed by ANN, showing R_v^2?=?0.7366 and RMSEV?=?0.7855.These higher determination coefficients reveal that both the non-K emission lines of wavelength dimension and the spectral decay of time dimension could assist in quantitative detection of K.However, due to limited calibration samples, the two-dimensional models presented over-fitting.The three-dimensional data of time-resolved LIBS were analyzed by CNNs, which extracted and integrated the information of both the wavelength and time dimension, showing the R_v^2?=?0.9968 and RMSEV?=?0.0785. CNN analysis of time-resolved LIBS is capable of improving the determination of K in soil.展开更多
To address the serious acoustic performance deterioration induced by air leakage in the low-frequency range and the asynchronous vibration in electroacoustic transduction structures near the resonant frequency,a novel...To address the serious acoustic performance deterioration induced by air leakage in the low-frequency range and the asynchronous vibration in electroacoustic transduction structures near the resonant frequency,a novel sealing strategy is proposed that targets one of the most widely reported piezoelectric MEMS speaker designs.This design consists of multiple cantilever beams,in which the air gaps between cantilevers are automatically and selectively filled with liquid polydimethylsiloxane(PDMS)via the capillary effect,followed by curing.In the proof-of-concept demonstration,the sound pressure level(SPL)within the frequency range lower than 100 Hz markedly increased after sealing in an experiment using an IEC ear simulator.Specifically,the SPL is increased by 4.9 dB at 20 Hz for a 40 Vpp driving voltage.Moreover,the deteriorated SPL response near the resonant frequencies of the cantilever beams(18 kHz–19 kHz)caused by their asynchronous vibration induced by the fabrication process nonuniformity also significantly improved,which successfully increased the SPL to approximately 17.5 dB.Moreover,sealed devices feature nearly the same SPL response as the initial counterpart in the frequency band from 100 Hz to 16 kHz and a total harmonic distortion(THD)of 0.728%at 1 kHz for a 40 Vpp driving voltage.Compared with existing sealing methods,the current approach offers easy operation,low damage risk,excellent repeatability/reliability and excellent robustness advantages and provides a promising technical solution for MEMS acoustic devices.展开更多
Optical-resolution photoacoustic microscopy(OR-PAM)is capable of observing the distribution of optical absorbers inside bio-tissues with a high spatial resolution of micrometers.Unfortunately,due to the employment of ...Optical-resolution photoacoustic microscopy(OR-PAM)is capable of observing the distribution of optical absorbers inside bio-tissues with a high spatial resolution of micrometers.Unfortunately,due to the employment of a tight optical focus,it suffers from a limited depth of field(DOF),making it challenging to achieve highresolution imaging of targets with arbitrary surfaces.Here,we propose a high spatiotemporal adaptive photoacoustic focusing mechanism through integrating a high-speed optical focuser,a time-of-flight contour deriving algorithm,and the rotary-scanning photoacoustic microscopy.The developed system,named high-speed adaptive photoacoustic microscopy(HA-PAM),features an ultrashort focus-shifting time of 5 ms and an enlarged DOF of up to 5 mm.With the assistance of the proposed mechanism,we can achieve a homogeneous lateral resolution of 6μm over a 10 mm circular imaging domain within 5 s.We demonstrate the advantages of HA-PAM through imaging phantoms with curved surfaces,subcutaneous tumor-bearing mice,resected rabbit kidneys,and pulsating mouse brains.The imaging results suggest that this approach provides a high and consistent spatial resolution for imaging bio-tissues with arbitrary surfaces without sacrificing the imaging speed,and has the potential to extend the fundamental and clinical applications of OR-PAM.展开更多
基金Project supported by the National Natural Science Foundation of China (No. 12002195)the National Science Fund for Distinguished Young Scholars (No. 12025204)the Program of Shanghai Municipal Education Commission (No. 2019-01-07-00-09-E00018)。
文摘The boundary value problem plays a crucial role in the analytical investigation of continuum dynamics. In this paper, an analytical method based on the Dirac operator to solve the nonlinear and non-homogeneous boundary value problem of rectangular plates is proposed. The key concept behind this method is to transform the nonlinear or non-homogeneous part on the boundary into a lateral force within the governing function by the Dirac operator, which linearizes and homogenizes the original boundary, allowing one to employ the modal superposition method for obtaining solutions to reconstructive governing equations. Once projected into the modal space, the harmonic balance method(HBM) is utilized to solve coupled ordinary differential equations(ODEs)of truncated systems with nonlinearity. To validate the convergence and accuracy of the proposed Dirac method, the results of typical examples, involving nonlinearly restricted boundaries, moment excitation, and displacement excitation, are compared with those of the differential quadrature element method(DQEM). The results demonstrate that when dealing with nonlinear boundaries, the Dirac method exhibits more excellent accuracy and convergence compared with the DQEM. However, when facing displacement excitation, there exist some discrepancies between the proposed approach and simulations;nevertheless, the proposed method still accurately predicts resonant frequencies while being uniquely capable of handling nonuniform displacement excitations. Overall, this methodology offers a convenient way for addressing nonlinear and non-homogenous plate boundaries.
基金supported by the National Natural Science Foundation of China(Nos.12072204,11972238)the Natural Science Foundation of Hebei Province of China(No.A2020210039)。
文摘The influence of pavement vibration on tire adhesion is of great significance to the structure design of vehicle and pavement.The adhesion between tire and road is the key to studying vehicle dynamics,and the precise description of tire adhesion affects the accuracy of dynamic vehicle responses.However,in most models,only road roughness is considered,and the pavement vibration caused by vehicle-road interaction is ignored.In this paper,a vehicle is simplified as a spring-mass-damper oscillator,and the vehicle-pavement system is modeled as a vehicle moving along an Euler-Bernoulli beam with finite length on a nonlinear foundation.The road roughness is considered as a sine wave,and the shear stress is ignored on the pavement.According to the contact form between tire and road,the LuGre tire model is established to calculate the tire adhesion force.The Galerkin method is used to simplify the partial differential equations of beam vibration into finite ordinary differential equations.A product-to-sum formula and a Dirac delt function are used to deal with the nonlinear term caused by the nonlinear foundation,which realizes the fast and accurate calculation of super-high dimensional nonlinear ordinary differential equations.In addition,the dynamic responses between the coupled system and the traditional uncoupled system are compared with each other.The obtained results provide an important theoretical basis for research on the influence of vehicle-road coupled vibration on tire adhesion.
基金supported by National Natural Science Foundation of China (Grant No. 61505253)National Key Research and Development Plan of China (Project No. 2016YFD0200601)
文摘One of the technical bottlenecks of traditional laser-induced breakdown spectroscopy(LIBS) is the difficulty in quantitative detection caused by the matrix effect. To troubleshoot this problem,this paper investigated a combination of time-resolved LIBS and convolutional neural networks(CNNs) to improve K determination in soil. The time-resolved LIBS contained the information of both wavelength and time dimension. The spectra of wavelength dimension showed the characteristic emission lines of elements, and those of time dimension presented the plasma decay trend. The one-dimensional data of LIBS intensity from the emission line at 766.49 nm were extracted and correlated with the K concentration, showing a poor correlation of R_c^2?=?0.0967, which is caused by the matrix effect of heterogeneous soil. For the wavelength dimension, the two-dimensional data of traditional integrated LIBS were extracted and analyzed by an artificial neural network(ANN), showing R_v^2?=?0.6318 and the root mean square error of validation(RMSEV)?=?0.6234. For the time dimension, the two-dimensional data of time-decay LIBS were extracted and analyzed by ANN, showing R_v^2?=?0.7366 and RMSEV?=?0.7855.These higher determination coefficients reveal that both the non-K emission lines of wavelength dimension and the spectral decay of time dimension could assist in quantitative detection of K.However, due to limited calibration samples, the two-dimensional models presented over-fitting.The three-dimensional data of time-resolved LIBS were analyzed by CNNs, which extracted and integrated the information of both the wavelength and time dimension, showing the R_v^2?=?0.9968 and RMSEV?=?0.0785. CNN analysis of time-resolved LIBS is capable of improving the determination of K in soil.
基金supported by the National Natural Science Foundation of China(NSFC)(12174137)the National Key Research and Development Plan of China(2020YFB2008800)the Innovation Project of Optics Valley Laboratory(Grant No.OVL2023ZD003).
文摘To address the serious acoustic performance deterioration induced by air leakage in the low-frequency range and the asynchronous vibration in electroacoustic transduction structures near the resonant frequency,a novel sealing strategy is proposed that targets one of the most widely reported piezoelectric MEMS speaker designs.This design consists of multiple cantilever beams,in which the air gaps between cantilevers are automatically and selectively filled with liquid polydimethylsiloxane(PDMS)via the capillary effect,followed by curing.In the proof-of-concept demonstration,the sound pressure level(SPL)within the frequency range lower than 100 Hz markedly increased after sealing in an experiment using an IEC ear simulator.Specifically,the SPL is increased by 4.9 dB at 20 Hz for a 40 Vpp driving voltage.Moreover,the deteriorated SPL response near the resonant frequencies of the cantilever beams(18 kHz–19 kHz)caused by their asynchronous vibration induced by the fabrication process nonuniformity also significantly improved,which successfully increased the SPL to approximately 17.5 dB.Moreover,sealed devices feature nearly the same SPL response as the initial counterpart in the frequency band from 100 Hz to 16 kHz and a total harmonic distortion(THD)of 0.728%at 1 kHz for a 40 Vpp driving voltage.Compared with existing sealing methods,the current approach offers easy operation,low damage risk,excellent repeatability/reliability and excellent robustness advantages and provides a promising technical solution for MEMS acoustic devices.
基金National Natural Science Foundation of China(61528401,61775028,62022037,81571722)Guangdong Science and Technology Department(2019ZT08Y191,SZBL2020090501013)+3 种基金Guangdong Provincial Department of Education(2021ZDZX1064)Guangdong Provincial Key Laboratory of Advanced Biomaterials(2022B1212010003)Shenzhen Science and Technology Program(JCYJ20200109141222892,KQTD20190929172743294)Start-up grant from Southern University of Science and Technology。
文摘Optical-resolution photoacoustic microscopy(OR-PAM)is capable of observing the distribution of optical absorbers inside bio-tissues with a high spatial resolution of micrometers.Unfortunately,due to the employment of a tight optical focus,it suffers from a limited depth of field(DOF),making it challenging to achieve highresolution imaging of targets with arbitrary surfaces.Here,we propose a high spatiotemporal adaptive photoacoustic focusing mechanism through integrating a high-speed optical focuser,a time-of-flight contour deriving algorithm,and the rotary-scanning photoacoustic microscopy.The developed system,named high-speed adaptive photoacoustic microscopy(HA-PAM),features an ultrashort focus-shifting time of 5 ms and an enlarged DOF of up to 5 mm.With the assistance of the proposed mechanism,we can achieve a homogeneous lateral resolution of 6μm over a 10 mm circular imaging domain within 5 s.We demonstrate the advantages of HA-PAM through imaging phantoms with curved surfaces,subcutaneous tumor-bearing mice,resected rabbit kidneys,and pulsating mouse brains.The imaging results suggest that this approach provides a high and consistent spatial resolution for imaging bio-tissues with arbitrary surfaces without sacrificing the imaging speed,and has the potential to extend the fundamental and clinical applications of OR-PAM.
