Target strength(TS)and circular synthetic aperture sonar(CSAS)images provide essential information for active acoustic detection and recognition of non-cooperative unmanned undersea vehicles(UUVs),which pose a signifi...Target strength(TS)and circular synthetic aperture sonar(CSAS)images provide essential information for active acoustic detection and recognition of non-cooperative unmanned undersea vehicles(UUVs),which pose a significant threat to underwater preset facilities.To access them,we propose an iterative physical acoustics(IPA)-based method to simulate the multiple acoustic scattered fields on rigid surfaces in high-frequency cases.It uses the Helmholtz integral equation with an appropriate Green's function in terms of the Neumann series,and then incorporates the ideas of triangulation and iteration into a numerical implementation.Then two approximate analytic formulae with precise physical meanings are derived to predict the TS and CSAS images of concave targets,respectively.There are no restrictions on the surface's curvature and the order of multiple scattering.The method is validated against the finite element method(FEM)for acoustic scattering from a sphere segment and against an experiment involving an X-rudder UUV's stern.On this basis,we simulate and analyze the TS and CSAS images of an X-rudder UUV.In addition,the influence of the angle of adjacent rudders on the multiple scattering characteristics is discussed.Results show that this method can potentially predict accurate UUV features,especially the multiple scattered features.展开更多
An exact solution based on the wavenumber integration method is proposed and implemented in a numerical model for the acoustic field in a Pekeris waveguide excited by either a point source in cylindrical geometry or a...An exact solution based on the wavenumber integration method is proposed and implemented in a numerical model for the acoustic field in a Pekeris waveguide excited by either a point source in cylindrical geometry or a line source in plane geometry. Besides, an unconditionally stable numerical solution is also presented, which entirely resolves the stability problem in previous methods. Generally the branch line integral contributes to the total field only at short ranges, and hence is usually ignored in traditional normal mode models. However, for the special case where a mode lies near the branch cut, the branch line integral can contribute to the total field significantly at all ranges. The wavenumber integration method is well-suited for such problems. Numerical results are also provided, which show that the present model can serve as a benchmark for sound propagation in a Pekeris waveguide.展开更多
Elasticity is of profound significance to evaluating the function of a biological soft tissue.When the elasticity of a tissue is macroscopically changed,it means that the biological function of the tissue is abnormal ...Elasticity is of profound significance to evaluating the function of a biological soft tissue.When the elasticity of a tissue is macroscopically changed,it means that the biological function of the tissue is abnormal and some disease or injury may occur.In the present work,an elastometer is developed to measure the elasticity of biological soft tissues.The measurement is based on the indentation method and the force is measured by the bending of the cantilever.The force-indentation data of the soft tissue is experimentally measured by this elastometer and Young's modulus of the tissue is calculated using the Hertz-Sneddon model.For comparison,a numerical model for the indentation method is established using the finite element method.The difference between the actual modulus and the measured modulus is discussed.The effect of the thickness of the specimen on the measurement is investigated.Young's moduli of beef,porcine liver and porcine kidney are experimentally measured.The results indicate that our elastometer is effective in measuring Young's modulus of a soft tissue quantitatively.展开更多
This paper presents a three-dimensional(3D) coupled-mode model using the direct-global-matrix technique as well as Fourier synthesis. This model is a full wave, two-way three-dimensional model, and is therefore capabl...This paper presents a three-dimensional(3D) coupled-mode model using the direct-global-matrix technique as well as Fourier synthesis. This model is a full wave, two-way three-dimensional model, and is therefore capable of providing accurate acoustic field solutions. Because the problem of sound propagation excited by a point source in an ideal wedge with perfectly reflecting boundaries is one of a few three-dimensional problems with analytical solutions, the ideal wedge problem is chosen in this work to validate the presented three-dimensional model. Numerical results show that the field results by analytical solutions and those by the presented model are in excellent agreement, indicating that the presented model can serve as a benchmark model for three-dimensional sound propagation problems involving a planar two-dimensional geometry as well as a point source.展开更多
The ultrashort intense laser pulse transmitted by a Nd:YAG laser system is used to generate the sound in ivater.Experiments show that the light beam is cojiverged by an optical lens at two points.This fact implies tha...The ultrashort intense laser pulse transmitted by a Nd:YAG laser system is used to generate the sound in ivater.Experiments show that the light beam is cojiverged by an optical lens at two points.This fact implies that,the time response is inherent bi the changes of optical index of water caused by the light intensity.展开更多
Complex perturbations in the profile and the sparsity of samples often limit the validity of rapid environmental assessment(REA)in the South China Sea(SCS).In this paper,the remote sensing data were used to estimate s...Complex perturbations in the profile and the sparsity of samples often limit the validity of rapid environmental assessment(REA)in the South China Sea(SCS).In this paper,the remote sensing data were used to estimate sound speed profile(SSP)with the self-organizing map(SOM)method in the SCS.First,the consistency of the empirical orthogonal functions was examined by using k-means clustering.The clustering results indicated that SSPs in the SCS have a similar perturbation nature,which means the inverted grid could be expanded to the entire SCS to deal with the problem of sparsity of the samples without statistical improbability.Second,a machine learning method was proposed that took advantage of the topological structure of SOM to significantly improve their accuracy.Validation revealed promising results,with a mean reconstruction error of 1.26 m/s,which is 1.16 m/s smaller than the traditional single empirical orthogonal function regression(sEOF-r)method.By violating the constraints of linear inversion,the topological structure of the SOM method showed a smaller error and better robustness in the SSP estimation.The improvements to enhance the accuracy and robustness of REA in the SCS were offered.These results suggested a potential utilization of REA in the SCS based on satellite data and provided a new approach for SSP estimation derived from sea surface data.展开更多
When deriving the Fourier diffraction theorem based on the first-order Born approximation,the difference between wave number of the scattering object and that of the surrounding medium is ignored,causing substantial e...When deriving the Fourier diffraction theorem based on the first-order Born approximation,the difference between wave number of the scattering object and that of the surrounding medium is ignored,causing substantial errors in sound scattering prediction.This paper modifies the Born approximation by taking into account the amplitude and phase changes between the scattering object and the water due to the wave number difference.By changing the radius and center position of the sampling circle in the Fourier domain,accuracy of the predicted sound scattering is improved.With the modified Born approximation,the computed far-field directional pattern of the scattered sound from a circular cylinder is in good agreement with the rigorous solution.Numerical calculations for several objects with different shapes are used to show applicability and effectiveness of the proposed method.展开更多
A numerically efficient broadband, range-dependent propagation model is proposed, which incorporates the Hamiltonian method into the coupled-mode model DGMCM. The Hamiltonian method is highly efficient for finding bro...A numerically efficient broadband, range-dependent propagation model is proposed, which incorporates the Hamiltonian method into the coupled-mode model DGMCM. The Hamiltonian method is highly efficient for finding broadband eigenvalues, and DGMCM is an accurate model for range-dependent propagation in the frequency domain. Consequently, the proposed broadband model combining the Hamiltonian method and DGMCM has significant virtue in terms of both efficiency and accuracy. Numerical simulations are also provided. The numerical results indicate that the proposed model has a better performance over the broadband model using the Fourier synthesis and COUPLE, while retaining the same level of accuracy.展开更多
The main goal of this study was to systematically investigate the relative contribution of spectral resolution and temporal envelope periodicity to musical pitch discrimination. Stimuli from four instruments(clarinet,...The main goal of this study was to systematically investigate the relative contribution of spectral resolution and temporal envelope periodicity to musical pitch discrimination. Stimuli from four instruments(clarinet,trumpet,piano and violin) and synthetic complex tone were utilized.A noise-excited vocoder was used to control the spectral resolution and temporal envelope periodicity of the musical stimuli.Ten normal-hearing subjects were recruited for the study.Psychoacoustic experiments on pitch discrimination were carried out.Results showed that the spectral cue was important for musical pitch discrimination.Relative good performance could be achieved when there were 16 frequency channels.No clear effect was found for the temporal envelope periodicity to pitch discrimination.展开更多
The main goal of this study was to systematically investigate place-pitch perception in electrical hearing and the relative relationship between place-pitch perception ability,speech understanding and musical pitch di...The main goal of this study was to systematically investigate place-pitch perception in electrical hearing and the relative relationship between place-pitch perception ability,speech understanding and musical pitch discrimination by cochlear implant(CI) users.Electrode pitch ranking test was carried out to evaluate the place-pitch perception ability of CI users. Four post-lingually deafened CI users were recruited.They also participated in the speech recognition test and musical pitch discrimination test.Results showed that place pitch were generally ordered from apical to basal electrodes.The apical electrodes were judged lower in pitch than basal electrodes.Large individual difference was found.Comparing pitch and speech performance,the speech recognition result was related to the place-pitch perception ability of CI users,but this relationship was limited by the ceiling effects.However,a correlative relationship was found between musical pitch discrimination result and place-pitch ability of CI users.It indicated that the current signal processing of CI system can provide sufficient information for speech understanding but not for music perception of CI users.To a certain extent,music perception of CI users was determined by their place-pitch abilities.展开更多
基金supported by the National Youth Science Foundation of China(Grant No.52001211).
文摘Target strength(TS)and circular synthetic aperture sonar(CSAS)images provide essential information for active acoustic detection and recognition of non-cooperative unmanned undersea vehicles(UUVs),which pose a significant threat to underwater preset facilities.To access them,we propose an iterative physical acoustics(IPA)-based method to simulate the multiple acoustic scattered fields on rigid surfaces in high-frequency cases.It uses the Helmholtz integral equation with an appropriate Green's function in terms of the Neumann series,and then incorporates the ideas of triangulation and iteration into a numerical implementation.Then two approximate analytic formulae with precise physical meanings are derived to predict the TS and CSAS images of concave targets,respectively.There are no restrictions on the surface's curvature and the order of multiple scattering.The method is validated against the finite element method(FEM)for acoustic scattering from a sphere segment and against an experiment involving an X-rudder UUV's stern.On this basis,we simulate and analyze the TS and CSAS images of an X-rudder UUV.In addition,the influence of the angle of adjacent rudders on the multiple scattering characteristics is discussed.Results show that this method can potentially predict accurate UUV features,especially the multiple scattered features.
基金supported by the National Natural Science Foundation of China(Grant No.11125420)the Knowledge Innovation Program of the Chinese Academy of Sciences+2 种基金the China Postdoctoral Science Foundation(Grant No.2014M561882)the Doctoral Fund of Shandong ProvinceChina(Grant No.BS2012HZ015)
文摘An exact solution based on the wavenumber integration method is proposed and implemented in a numerical model for the acoustic field in a Pekeris waveguide excited by either a point source in cylindrical geometry or a line source in plane geometry. Besides, an unconditionally stable numerical solution is also presented, which entirely resolves the stability problem in previous methods. Generally the branch line integral contributes to the total field only at short ranges, and hence is usually ignored in traditional normal mode models. However, for the special case where a mode lies near the branch cut, the branch line integral can contribute to the total field significantly at all ranges. The wavenumber integration method is well-suited for such problems. Numerical results are also provided, which show that the present model can serve as a benchmark for sound propagation in a Pekeris waveguide.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11274342,11304353,11404245 and 11474042
文摘Elasticity is of profound significance to evaluating the function of a biological soft tissue.When the elasticity of a tissue is macroscopically changed,it means that the biological function of the tissue is abnormal and some disease or injury may occur.In the present work,an elastometer is developed to measure the elasticity of biological soft tissues.The measurement is based on the indentation method and the force is measured by the bending of the cantilever.The force-indentation data of the soft tissue is experimentally measured by this elastometer and Young's modulus of the tissue is calculated using the Hertz-Sneddon model.For comparison,a numerical model for the indentation method is established using the finite element method.The difference between the actual modulus and the measured modulus is discussed.The effect of the thickness of the specimen on the measurement is investigated.Young's moduli of beef,porcine liver and porcine kidney are experimentally measured.The results indicate that our elastometer is effective in measuring Young's modulus of a soft tissue quantitatively.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11125420,11434012,and 41561144006)the Knowledge Innovation Program of the Chinese Academy of Sciences
文摘This paper presents a three-dimensional(3D) coupled-mode model using the direct-global-matrix technique as well as Fourier synthesis. This model is a full wave, two-way three-dimensional model, and is therefore capable of providing accurate acoustic field solutions. Because the problem of sound propagation excited by a point source in an ideal wedge with perfectly reflecting boundaries is one of a few three-dimensional problems with analytical solutions, the ideal wedge problem is chosen in this work to validate the presented three-dimensional model. Numerical results show that the field results by analytical solutions and those by the presented model are in excellent agreement, indicating that the presented model can serve as a benchmark model for three-dimensional sound propagation problems involving a planar two-dimensional geometry as well as a point source.
基金Supported by the National Natural Science Foundation of Chinathe Laboratory of Modern Acoustics of Nanjing University.
文摘The ultrashort intense laser pulse transmitted by a Nd:YAG laser system is used to generate the sound in ivater.Experiments show that the light beam is cojiverged by an optical lens at two points.This fact implies that,the time response is inherent bi the changes of optical index of water caused by the light intensity.
基金The Natural Science Foundation of Guangdong Province under contract No.2022A1515011519the National Natural Science Foundation of China under contract No.11904290.
文摘Complex perturbations in the profile and the sparsity of samples often limit the validity of rapid environmental assessment(REA)in the South China Sea(SCS).In this paper,the remote sensing data were used to estimate sound speed profile(SSP)with the self-organizing map(SOM)method in the SCS.First,the consistency of the empirical orthogonal functions was examined by using k-means clustering.The clustering results indicated that SSPs in the SCS have a similar perturbation nature,which means the inverted grid could be expanded to the entire SCS to deal with the problem of sparsity of the samples without statistical improbability.Second,a machine learning method was proposed that took advantage of the topological structure of SOM to significantly improve their accuracy.Validation revealed promising results,with a mean reconstruction error of 1.26 m/s,which is 1.16 m/s smaller than the traditional single empirical orthogonal function regression(sEOF-r)method.By violating the constraints of linear inversion,the topological structure of the SOM method showed a smaller error and better robustness in the SSP estimation.The improvements to enhance the accuracy and robustness of REA in the SCS were offered.These results suggested a potential utilization of REA in the SCS based on satellite data and provided a new approach for SSP estimation derived from sea surface data.
基金supported by the National Natural Science Foundation of China(61071187)Key Laboratory Foundation for Underwater Test and Control Technology(9140c260201110c26)
文摘When deriving the Fourier diffraction theorem based on the first-order Born approximation,the difference between wave number of the scattering object and that of the surrounding medium is ignored,causing substantial errors in sound scattering prediction.This paper modifies the Born approximation by taking into account the amplitude and phase changes between the scattering object and the water due to the wave number difference.By changing the radius and center position of the sampling circle in the Fourier domain,accuracy of the predicted sound scattering is improved.With the modified Born approximation,the computed far-field directional pattern of the scattered sound from a circular cylinder is in good agreement with the rigorous solution.Numerical calculations for several objects with different shapes are used to show applicability and effectiveness of the proposed method.
基金supported by the National Natural Science Foundation of China(Grant No.11125420)the Knowledge Innovation Program of the Chinese Academy of Sciences
文摘A numerically efficient broadband, range-dependent propagation model is proposed, which incorporates the Hamiltonian method into the coupled-mode model DGMCM. The Hamiltonian method is highly efficient for finding broadband eigenvalues, and DGMCM is an accurate model for range-dependent propagation in the frequency domain. Consequently, the proposed broadband model combining the Hamiltonian method and DGMCM has significant virtue in terms of both efficiency and accuracy. Numerical simulations are also provided. The numerical results indicate that the proposed model has a better performance over the broadband model using the Fourier synthesis and COUPLE, while retaining the same level of accuracy.
基金supported by the Chinese Academy of Sciences Pilot Project of the Knowledge Innovation Program(KGCX2-YX-607)Key Projects in the National Science & Technology Pillar Program in the Eleventh Five-year Plan Period(2008BAI50B08)+1 种基金National Natural Science Foundation of China(11104316)Shanghai Natural Science Foundation(11ZR1446000)
文摘The main goal of this study was to systematically investigate the relative contribution of spectral resolution and temporal envelope periodicity to musical pitch discrimination. Stimuli from four instruments(clarinet,trumpet,piano and violin) and synthetic complex tone were utilized.A noise-excited vocoder was used to control the spectral resolution and temporal envelope periodicity of the musical stimuli.Ten normal-hearing subjects were recruited for the study.Psychoacoustic experiments on pitch discrimination were carried out.Results showed that the spectral cue was important for musical pitch discrimination.Relative good performance could be achieved when there were 16 frequency channels.No clear effect was found for the temporal envelope periodicity to pitch discrimination.
基金supported by the Chinese Academy of Sciences Pilot Project of the Knowledge Innovation Program(KGCX2-YX-607)Key Projects in the National Science & Technology Pillar Program in the Eleventh Five-year Plan Period(2008BAI50B08)+1 种基金National Natural Science Foundation of China(11104316)Shanghai Natural Science Foundation(11ZR1446000)
文摘The main goal of this study was to systematically investigate place-pitch perception in electrical hearing and the relative relationship between place-pitch perception ability,speech understanding and musical pitch discrimination by cochlear implant(CI) users.Electrode pitch ranking test was carried out to evaluate the place-pitch perception ability of CI users. Four post-lingually deafened CI users were recruited.They also participated in the speech recognition test and musical pitch discrimination test.Results showed that place pitch were generally ordered from apical to basal electrodes.The apical electrodes were judged lower in pitch than basal electrodes.Large individual difference was found.Comparing pitch and speech performance,the speech recognition result was related to the place-pitch perception ability of CI users,but this relationship was limited by the ceiling effects.However,a correlative relationship was found between musical pitch discrimination result and place-pitch ability of CI users.It indicated that the current signal processing of CI system can provide sufficient information for speech understanding but not for music perception of CI users.To a certain extent,music perception of CI users was determined by their place-pitch abilities.
