The problem of three-dimensional(3D) acoustic scattering in a complex medium has aroused considerable interest of researchers for many years. An ultrasonic scattered field calculating technique is proposed to study th...The problem of three-dimensional(3D) acoustic scattering in a complex medium has aroused considerable interest of researchers for many years. An ultrasonic scattered field calculating technique is proposed to study the scattering echo from strongly scattered materials in a two-layer medium in this work. Firstly, with the high frequency stationary phase method,the Green's function of two-layer fluid media is derived. And then based on the idea of integral equation discretization,the Green's function method is extended to two-layer fluid media to derive the scattering field expression of defects in a complex medium. With this method, the scattering field of 3D defect in a two-layer medium is calculated and the characteristics of received echoes are studied. The results show that this method is able to solve the scattering P wave field of 3D defect with arbitrary shape at any scattering intensity in two-layer media. Considering the circumstance of waterimmersion ultrasonic non-destructive test(NDT), the scattering sound field characteristics of different types of defects are analyzed by simulation, which will help to optimize the detection scheme and corresponding imaging method in practice so as to improve the detection quality.展开更多
The finite volume time domain(FVTD) algorithm and Green function algorithm are extended to Schwarzschild spacetime for numerical simulation of electromagnetic scattering. The FVTD method in Schwarzschild spacetime is ...The finite volume time domain(FVTD) algorithm and Green function algorithm are extended to Schwarzschild spacetime for numerical simulation of electromagnetic scattering. The FVTD method in Schwarzschild spacetime is developed by filling the flat spacetime with an equivalent medium. The Green function in Schwarzschild spacetime is acquired by solving initial value problems. Both the FVTD code and the Green function code are validated by numerical results. Scattering in Schwarzschild spacetime is simulated with these methods.展开更多
At first the bitemporal response method is introd uced to solve the scattering function of the ionospheric channel. We can get the scattering function as a function of the group path time delay and Doppler freq uency....At first the bitemporal response method is introd uced to solve the scattering function of the ionospheric channel. We can get the scattering function as a function of the group path time delay and Doppler freq uency. Thus Doppler effect resulting from the continuous movement of the ionosp here is analyzed to study the characteristics of the various ionospheric irregul arities and disturbance. many possible problems and correction are rese arched lastly.展开更多
The theory of elastic wave scattering is a fundamental concept in the study of elastic dynamics and wave motion,and the wave function expansion technique has been widely used in many subjects.To supply the essential t...The theory of elastic wave scattering is a fundamental concept in the study of elastic dynamics and wave motion,and the wave function expansion technique has been widely used in many subjects.To supply the essential tools for solving wave scattering problems induced by an eccentric source or multi-sources as well as multi-scatters,a whole-space transform formula of cylindrical wave functions is presented and its applicability to some simple cases is demonstrated in this study.The transforms of wave functions in cylindrical coordinates can be classifi ed into two basic types: interior transform and exterior transform,and the existing Graf's addition theorem is only suitable for the former.By performing a new replacement between the two coordinates,the exterior transform formula is fi rst deduced.It is then combined with Graf's addition theorem to establish a whole-space transform formula.By using the whole-space transform formula,the scattering solutions by the sources outside and inside a cylindrical cavity are constructed as examples of its application.The effectiveness and advantages of the whole-space transform formula is illustrated by comparison with the approximate model based on a large cycle method.The whole-space transform formula presented herein can be used to perform the transform between two different cylindrical coordinates in the whole space.In addition,its concept and principle are universal and can be further extended to establish the coordinate transform formula of wave functions in other coordinate systems.展开更多
Functionalized nano-PbS has been prepared and characterized. The functionalized nanoparticles have good dispersibility in water. Reaction of functionalized nanoPbS with gglobulin (gIgG) results an enhanced resonance l...Functionalized nano-PbS has been prepared and characterized. The functionalized nanoparticles have good dispersibility in water. Reaction of functionalized nanoPbS with gglobulin (gIgG) results an enhanced resonance light scattering (RLS) around 385 nm. However, when the content of HSA is lower than 0.5 mg ml-1 the RLS enhancement is very weak and is nonlinear to concentration of HSA. Based on these results, a new direct quantitative determination method for gglobulin in blood serum samples without separation is established. Under optimal conditions, the enhanced RLS intensity is in proportion to the gIgG concentration in the range 10500 ng/mL. The limit of detection is 2.75 ng/mL. This method is proved to be very sensitive, rapid, simple and selective for detection of gIgG in blood serum.展开更多
For a system of flexible polymer molecules, the concepts of two concentrations, namely the segmental and the molecular concentrations, have been proposed in this paper. The former is equivalent to the volume fraction....For a system of flexible polymer molecules, the concepts of two concentrations, namely the segmental and the molecular concentrations, have been proposed in this paper. The former is equivalent to the volume fraction. The latter can be defined as the number of the gravity centers of macromolecules in a unit volume. The two concentrations should be correlated with each other by the conformational function of the polymer chain and should be discussed in different thermodynamic equations. On the basis of these concepts it has been proved that the Flory-Huggins entropy of mixing should be the result of the mixing "ideal gases of the gravity centers of macromolecules". The general correlation between the free energy of mixing and the scattering function (structural factor) of polymer blends has been studied based on the general fluctuation theory. When the Flory-Huggins free energy of mixing is adopted, the de Gennes scattering function of a polymer blend can be derived.展开更多
When the finite difference time domain(FDTD) method is used to solve electromagnetic scattering problems in Schwarzschild space-time, the Green functions linking source/observer to every surface element on connection/...When the finite difference time domain(FDTD) method is used to solve electromagnetic scattering problems in Schwarzschild space-time, the Green functions linking source/observer to every surface element on connection/output boundary must be calculated.When the scatterer is electrically extended, a huge amount of calculation is required due to a large number of surface elements on the connection/output boundary.In this paper, a method for reducing the calculation workload of Green function is proposed.The Taylor approximation is applied for the calculation of Green function.New transport equations are deduced.The numerical results verify the effectiveness of this method.展开更多
An analysis of solving the electromagnetic scattering by buried objects using vectorwave function expansion is presented.For expanding the boundary conditions both on the planarair-earth interface and on the spherical...An analysis of solving the electromagnetic scattering by buried objects using vectorwave function expansion is presented.For expanding the boundary conditions both on the planarair-earth interface and on the spherical surface,the conversion relations between the cylindricaland spherical vector wave functions are derived.Hence the vector wave function expansion isconveniently applied to solve this complex boundary-value problem.For the excitation of the in-cident plane wave and the dipole above the earth,the scatterlng patterns of the buried conductingand dielectric spheres are presented and discussed.展开更多
The multilevel characteristic basis function method(MLCBFM)with the adaptive cross approximation(ACA)algorithm for accelerated solution of electrically large scattering problems is studied in this paper.In the convent...The multilevel characteristic basis function method(MLCBFM)with the adaptive cross approximation(ACA)algorithm for accelerated solution of electrically large scattering problems is studied in this paper.In the conventional MLCBFM based on Foldy-Lax multiple scattering equations,the improvement is only made in the generation of characteristic basis functions(CBFs).However,it does not provide a change in impedance matrix filling and reducing matrix calculation procedure,which is time-consuming.In reality,all the impedance and reduced matrix of each level of the MLCBFM have low-rank property and can be calculated efficiently.Therefore,ACA is used for the efficient generation of two-level CBFs and the fast calculation of reduced matrix in this study.Numerical results are given to demonstrate the accuracy and efficiency of the method.展开更多
The research considers wavelike objects that are elements of even subalgebra of geometric algebra in three dimensions. The used formalism particularly eliminates long existing confusion about the reasons behind the ap...The research considers wavelike objects that are elements of even subalgebra of geometric algebra in three dimensions. The used formalism particularly eliminates long existing confusion about the reasons behind the appearance of the imaginary unit in quantum mechanics and introduces clear definition of wave functions. When a wave function acts through the Hopf fibration on a localized geometric algebra element, that is executing a measurement, the result can be named as “collapse” of the wave function.展开更多
To accelerate head-related transfer functions(HRTFs)measurement,two or more independent sound sources are usually employed in the measurement system.However,the multiple scattering between adjacent sound sources may i...To accelerate head-related transfer functions(HRTFs)measurement,two or more independent sound sources are usually employed in the measurement system.However,the multiple scattering between adjacent sound sources may influence the accuracy of measurement.On the other hand,the directivity of sound source could induce measurement error.Therefore,a model consisting of two spherical sound sources with approximate omni-directivity and a rigid-spherical head is proposed to evaluate the errors in HRTF measurement caused by multiple scattering between sources.An example of analysis using multipole re-expansion indicates that the error of ipsilateral HRTFs are within the bound of±1.0 dB below a frequency of 20 kHz,provided that the sound source radius does not exceed 0.025 m,the source distance relative to head center is not less than 0.5 m,and the angular interval between two adjacent sources is not less than 20 degrees.Similar conclusions under different conditions can also be analyzed and discussed by using this calculation method.Furthermore,the results are verified by measurements of HRTFs for a rigid sphere and a KEMAR artificial head.展开更多
The atmospheric scattering optical transfer function(OTF) is solved by applying the multi-coupled single scattering(MCSS) method to the three-dimensional radiative transfer equation(RTE) under the periodic ground cond...The atmospheric scattering optical transfer function(OTF) is solved by applying the multi-coupled single scattering(MCSS) method to the three-dimensional radiative transfer equation(RTE) under the periodic ground condition. This approach is a direct hit to the atmospheric scattering OTF using the same original context of modulation transfer function(MTF) measurement, i.e., images of sinusoidal grating at different spatial frequencies. Both the amplitude and phase shift of the OTF at various zenith and azimuth angles can be obtained at an arbitrary spatial frequency.展开更多
Acoustic scattering from a rough sea bottom is recognized as a main source of reverberation. In this study, scattering properties from a layered bottom were exploited based on the finite element model. The scattering ...Acoustic scattering from a rough sea bottom is recognized as a main source of reverberation. In this study, scattering properties from a layered bottom were exploited based on the finite element model. The scattering strength and loss from the layered rough seabed were investigated by ensembling the realizations of rough interface. They were found to be dependent on the thickness of sediment, and interference was significant in the case of thin sediment. Through verification of the finite element model, the scattering loss could be evaluated using the Eckart model with a proper sound speed in the thick sediment. The multiple scattering effect on the sound field was also exploited. It revealed that the effect depended strongly on the bottom type.展开更多
The elastic scattering of 162 MeV л± from <sup>13</sup>C and the excitation function of <sup>13</sup>C(л<sup>+</sup>,л<sup>0</sup>)<sup>13</sup>N a...The elastic scattering of 162 MeV л± from <sup>13</sup>C and the excitation function of <sup>13</sup>C(л<sup>+</sup>,л<sup>0</sup>)<sup>13</sup>N are analyzed in the frame of the Glauber theory.The nuclear wave function is assumedto be constructed by a valence nucleon plus a core of <sup>12</sup>C which is described by an independent αcluster model.A good agreement between the theory and experiment is obtained.展开更多
The Green’s function is used to solve the scattering far field solution of SH-wave by a mov-able rigid cylindrical interface inclusion in a linear elastic body.First,a suitable Green’s function is devel-oped,which i...The Green’s function is used to solve the scattering far field solution of SH-wave by a mov-able rigid cylindrical interface inclusion in a linear elastic body.First,a suitable Green’s function is devel-oped,which is the fundamental displacement solution of an elastic half space with a movable rigid half-cylin-drical inclusion impacted by out-of-plane harmonic line source loaded at any point of its horizontal surface.By using the Green’s function,a series of Fredholm integral equations of the first kind which determine thescattering far field can be set up.Then the paper gives the expressions on the far field including the displace-ment mode of scattering wave and the solution of scattering cross-section.Finally,some examples and nu-merical results are discussed to analyze the influence of the combination of different media parameters on theanswer of far field.展开更多
基金Project supported by the Key Research Program of Frontier Sciences, Chinese Academy of Sciences (Grant No. ZDBS-LY-7023)。
文摘The problem of three-dimensional(3D) acoustic scattering in a complex medium has aroused considerable interest of researchers for many years. An ultrasonic scattered field calculating technique is proposed to study the scattering echo from strongly scattered materials in a two-layer medium in this work. Firstly, with the high frequency stationary phase method,the Green's function of two-layer fluid media is derived. And then based on the idea of integral equation discretization,the Green's function method is extended to two-layer fluid media to derive the scattering field expression of defects in a complex medium. With this method, the scattering field of 3D defect in a two-layer medium is calculated and the characteristics of received echoes are studied. The results show that this method is able to solve the scattering P wave field of 3D defect with arbitrary shape at any scattering intensity in two-layer media. Considering the circumstance of waterimmersion ultrasonic non-destructive test(NDT), the scattering sound field characteristics of different types of defects are analyzed by simulation, which will help to optimize the detection scheme and corresponding imaging method in practice so as to improve the detection quality.
基金Supported by the National Natural Science Foundation of China under Grant No 61601105
文摘The finite volume time domain(FVTD) algorithm and Green function algorithm are extended to Schwarzschild spacetime for numerical simulation of electromagnetic scattering. The FVTD method in Schwarzschild spacetime is developed by filling the flat spacetime with an equivalent medium. The Green function in Schwarzschild spacetime is acquired by solving initial value problems. Both the FVTD code and the Green function code are validated by numerical results. Scattering in Schwarzschild spacetime is simulated with these methods.
基金Supported by the National Natural Science Foundation of China(6 95 710 2 0 ) and the Research Fund for the Doctoral Program of H
文摘At first the bitemporal response method is introd uced to solve the scattering function of the ionospheric channel. We can get the scattering function as a function of the group path time delay and Doppler freq uency. Thus Doppler effect resulting from the continuous movement of the ionosp here is analyzed to study the characteristics of the various ionospheric irregul arities and disturbance. many possible problems and correction are rese arched lastly.
基金the National Natural Science Foundation of China under Grand No.549974011
文摘The theory of elastic wave scattering is a fundamental concept in the study of elastic dynamics and wave motion,and the wave function expansion technique has been widely used in many subjects.To supply the essential tools for solving wave scattering problems induced by an eccentric source or multi-sources as well as multi-scatters,a whole-space transform formula of cylindrical wave functions is presented and its applicability to some simple cases is demonstrated in this study.The transforms of wave functions in cylindrical coordinates can be classifi ed into two basic types: interior transform and exterior transform,and the existing Graf's addition theorem is only suitable for the former.By performing a new replacement between the two coordinates,the exterior transform formula is fi rst deduced.It is then combined with Graf's addition theorem to establish a whole-space transform formula.By using the whole-space transform formula,the scattering solutions by the sources outside and inside a cylindrical cavity are constructed as examples of its application.The effectiveness and advantages of the whole-space transform formula is illustrated by comparison with the approximate model based on a large cycle method.The whole-space transform formula presented herein can be used to perform the transform between two different cylindrical coordinates in the whole space.In addition,its concept and principle are universal and can be further extended to establish the coordinate transform formula of wave functions in other coordinate systems.
文摘Functionalized nano-PbS has been prepared and characterized. The functionalized nanoparticles have good dispersibility in water. Reaction of functionalized nanoPbS with gglobulin (gIgG) results an enhanced resonance light scattering (RLS) around 385 nm. However, when the content of HSA is lower than 0.5 mg ml-1 the RLS enhancement is very weak and is nonlinear to concentration of HSA. Based on these results, a new direct quantitative determination method for gglobulin in blood serum samples without separation is established. Under optimal conditions, the enhanced RLS intensity is in proportion to the gIgG concentration in the range 10500 ng/mL. The limit of detection is 2.75 ng/mL. This method is proved to be very sensitive, rapid, simple and selective for detection of gIgG in blood serum.
基金This research was supported by the National Natural Science Foundation of China under Grant Nos. 40405001 and 40490261by the Climate Change Special Fund No. CCSF2005-3-DH15 from the China Meteorological Administration.
基金This work was supported by the special funds for major state basic research project of China (Grant No.G1999064808) andby 863-project
文摘For a system of flexible polymer molecules, the concepts of two concentrations, namely the segmental and the molecular concentrations, have been proposed in this paper. The former is equivalent to the volume fraction. The latter can be defined as the number of the gravity centers of macromolecules in a unit volume. The two concentrations should be correlated with each other by the conformational function of the polymer chain and should be discussed in different thermodynamic equations. On the basis of these concepts it has been proved that the Flory-Huggins entropy of mixing should be the result of the mixing "ideal gases of the gravity centers of macromolecules". The general correlation between the free energy of mixing and the scattering function (structural factor) of polymer blends has been studied based on the general fluctuation theory. When the Flory-Huggins free energy of mixing is adopted, the de Gennes scattering function of a polymer blend can be derived.
基金Project supported by the National Natural Science Foundation of China(Grant No.61601105)
文摘When the finite difference time domain(FDTD) method is used to solve electromagnetic scattering problems in Schwarzschild space-time, the Green functions linking source/observer to every surface element on connection/output boundary must be calculated.When the scatterer is electrically extended, a huge amount of calculation is required due to a large number of surface elements on the connection/output boundary.In this paper, a method for reducing the calculation workload of Green function is proposed.The Taylor approximation is applied for the calculation of Green function.New transport equations are deduced.The numerical results verify the effectiveness of this method.
基金This work is supported by the National Natural Science Foundation of China
文摘An analysis of solving the electromagnetic scattering by buried objects using vectorwave function expansion is presented.For expanding the boundary conditions both on the planarair-earth interface and on the spherical surface,the conversion relations between the cylindricaland spherical vector wave functions are derived.Hence the vector wave function expansion isconveniently applied to solve this complex boundary-value problem.For the excitation of the in-cident plane wave and the dipole above the earth,the scatterlng patterns of the buried conductingand dielectric spheres are presented and discussed.
基金supported by the National Natural Science Foundation of China (No.61401003)the Specialized Research Fund for the Doctoral Program of Higher Education of China (No.20123401110006)the Natural Science Research Project of Anhui Education ( No. KJ2015A436)
文摘The multilevel characteristic basis function method(MLCBFM)with the adaptive cross approximation(ACA)algorithm for accelerated solution of electrically large scattering problems is studied in this paper.In the conventional MLCBFM based on Foldy-Lax multiple scattering equations,the improvement is only made in the generation of characteristic basis functions(CBFs).However,it does not provide a change in impedance matrix filling and reducing matrix calculation procedure,which is time-consuming.In reality,all the impedance and reduced matrix of each level of the MLCBFM have low-rank property and can be calculated efficiently.Therefore,ACA is used for the efficient generation of two-level CBFs and the fast calculation of reduced matrix in this study.Numerical results are given to demonstrate the accuracy and efficiency of the method.
文摘The research considers wavelike objects that are elements of even subalgebra of geometric algebra in three dimensions. The used formalism particularly eliminates long existing confusion about the reasons behind the appearance of the imaginary unit in quantum mechanics and introduces clear definition of wave functions. When a wave function acts through the Hopf fibration on a localized geometric algebra element, that is executing a measurement, the result can be named as “collapse” of the wave function.
基金funded by National Natural Science Foundation of China(No.11574090)Natural Science Foundation of Guangdong Province(No.2018B030311025).
文摘To accelerate head-related transfer functions(HRTFs)measurement,two or more independent sound sources are usually employed in the measurement system.However,the multiple scattering between adjacent sound sources may influence the accuracy of measurement.On the other hand,the directivity of sound source could induce measurement error.Therefore,a model consisting of two spherical sound sources with approximate omni-directivity and a rigid-spherical head is proposed to evaluate the errors in HRTF measurement caused by multiple scattering between sources.An example of analysis using multipole re-expansion indicates that the error of ipsilateral HRTFs are within the bound of±1.0 dB below a frequency of 20 kHz,provided that the sound source radius does not exceed 0.025 m,the source distance relative to head center is not less than 0.5 m,and the angular interval between two adjacent sources is not less than 20 degrees.Similar conclusions under different conditions can also be analyzed and discussed by using this calculation method.Furthermore,the results are verified by measurements of HRTFs for a rigid sphere and a KEMAR artificial head.
基金supported by the Main Direction Program of Knowledge Innovation of Chinese Academy of Sciences(Grant No.KGFZD-125-13-006)
文摘The atmospheric scattering optical transfer function(OTF) is solved by applying the multi-coupled single scattering(MCSS) method to the three-dimensional radiative transfer equation(RTE) under the periodic ground condition. This approach is a direct hit to the atmospheric scattering OTF using the same original context of modulation transfer function(MTF) measurement, i.e., images of sinusoidal grating at different spatial frequencies. Both the amplitude and phase shift of the OTF at various zenith and azimuth angles can be obtained at an arbitrary spatial frequency.
基金Project supported by the National Natural Science Foundation of China(Grant No.61571366)the Natural Science Basic Research in Shaanxi Province of China(Grant No.2015JQ5199)the Fund of Science and Technology from the Underwater Test and Control Laboratory(Grant No.9140c260201130c26096)
文摘Acoustic scattering from a rough sea bottom is recognized as a main source of reverberation. In this study, scattering properties from a layered bottom were exploited based on the finite element model. The scattering strength and loss from the layered rough seabed were investigated by ensembling the realizations of rough interface. They were found to be dependent on the thickness of sediment, and interference was significant in the case of thin sediment. Through verification of the finite element model, the scattering loss could be evaluated using the Eckart model with a proper sound speed in the thick sediment. The multiple scattering effect on the sound field was also exploited. It revealed that the effect depended strongly on the bottom type.
基金The project supported by the National Natural Science Foundation of ChinaChina Postdoctoral Science Foundation(Lei Yian)
文摘The elastic scattering of 162 MeV л± from <sup>13</sup>C and the excitation function of <sup>13</sup>C(л<sup>+</sup>,л<sup>0</sup>)<sup>13</sup>N are analyzed in the frame of the Glauber theory.The nuclear wave function is assumedto be constructed by a valence nucleon plus a core of <sup>12</sup>C which is described by an independent αcluster model.A good agreement between the theory and experiment is obtained.
文摘The Green’s function is used to solve the scattering far field solution of SH-wave by a mov-able rigid cylindrical interface inclusion in a linear elastic body.First,a suitable Green’s function is devel-oped,which is the fundamental displacement solution of an elastic half space with a movable rigid half-cylin-drical inclusion impacted by out-of-plane harmonic line source loaded at any point of its horizontal surface.By using the Green’s function,a series of Fredholm integral equations of the first kind which determine thescattering far field can be set up.Then the paper gives the expressions on the far field including the displace-ment mode of scattering wave and the solution of scattering cross-section.Finally,some examples and nu-merical results are discussed to analyze the influence of the combination of different media parameters on theanswer of far field.