Because most piezoelectric devices have interfaces with fluid in engineering, it is valuable to study the coupled field between fluid and piezoelectric media. As the fundamental problem, the 3D Green's functions for ...Because most piezoelectric devices have interfaces with fluid in engineering, it is valuable to study the coupled field between fluid and piezoelectric media. As the fundamental problem, the 3D Green's functions for point forces and point charge loaded in the fluid and piezoelectric bimaterials are studied in this paper. Based on the 3D general solutions expressed by harmonic functions, we constructed the suitable harmonic functions with undetermined constants at first. Then, the couple field in the fluid and piezoelectric bimaterials can be derived by substitution of harmonic functions into general solutions. These constants can be obtained by virtue of the compatibility, boundary, and equilibrium conditions. At last, the characteristics of the electromechanical coupled fields are shown by numerical results.展开更多
With dense seismic arrays and advanced imaging methods, regional three-dimensional (3D) Earth models have become more accurate. It is now increasingly feasible and advantageous to use a 3D Earth model to better loca...With dense seismic arrays and advanced imaging methods, regional three-dimensional (3D) Earth models have become more accurate. It is now increasingly feasible and advantageous to use a 3D Earth model to better locate earthquakes and invert their source mechanisms by fitting synthetics to observed waveforms. In this study, we develop an approach to determine both the earthquake location and source mechanism from waveform information. The observed waveforms are filtered in different frequency bands and separated into windows for the individual phases. Instead of picking the arrival times, the traveltime differences are measured by cross-correlation between synthetic waveforms based on the 3D Earth model and observed waveforms. The earthquake location is determined by minimizing the cross-correlation traveltime differences. We then fix the horizontal location of the earthquake and perform a grid search in depth to determine the source mechanism at each point by fitting the synthetic and observed waveforms. This new method is verified by a synthetic test with noise added to the synthetic waveforms and a realistic station distribution. We apply this method to a series of Mw3.4-5.6 earthquakes in the Longmenshan fault (LMSF) zone, a region with rugged topography between the eastern margin of the Tibetan plateau and the western part of the Sichuan basin. The results show that our solutions result in improved waveform fits compared to the source parameters from the catalogs we used and the location can be better constrained than the amplitude-only approach. Furthermore, the source solutions with realistic topography provide a better fit to the observed waveforms than those without the topography, indicating the need to take the topography into account in regions with rugged topography.展开更多
Since the 18 th National Congress of the Communist Party of China,General Secretary Xi Jinping delivered a series of speeches on ecological environment and poverty governance,forming the Xi Jinping s eco-poverty allev...Since the 18 th National Congress of the Communist Party of China,General Secretary Xi Jinping delivered a series of speeches on ecological environment and poverty governance,forming the Xi Jinping s eco-poverty alleviation ideology.In this paper,the Xi Jinping s eco-poverty alleviation ideology is taken as the research object.Using the methods of literature analysis and comparative analysis,the origin of eco-poverty alleviation theory is explored from the common prosperity theory and the theory of ecological capital,and the practice foundation is found out from practical cases.The relationship between the ecological damage and poverty is systematically analyzed,and the mechanism of ecological poverty is explored in detail.The basic connotation of Xi Jinping s eco-poverty alleviation is expounded,and it consists of three parts:guiding ideology layer,implementation layer,and guarantee layer.By perfecting and innovating the market mechanism,social management mechanism,performance evaluation mechanism,integration mechanism with other poverty alleviation methods,and ecological immigration mechanism of ecological poverty,the realization of Xi Jinping s eco-poverty alleviation concept could be guaranteed.展开更多
Warthin’s tumor is the second most frequent neoplasm next to pleomorphic adenoma in the salivary gland. The tumor contains the epithelial oncocyte cells with the presence of rich-mitochondria and their surrounding ab...Warthin’s tumor is the second most frequent neoplasm next to pleomorphic adenoma in the salivary gland. The tumor contains the epithelial oncocyte cells with the presence of rich-mitochondria and their surrounding abundant lymphocytes. A relatively new disease entity of IgG4-related disease frequently occurs in the salivary gland. However, the coexistence of Warthin’s tumor and IgG4-related disease is scarcely observed. We have recently experienced a rare case of Warthin’s tumor with IgG4-related sialadenitis. A 51-year-old man presented to our hospital, complaining of a mass with right submandibular tenderness and spontaneous pain. A computed tomography scan of the cervical region revealed a suspicion of lymph node proliferative disease, including malignant lymphoma. Elevated serum levels of IL-2R: 1843 U/ml (reference value 122 - 496 U/ml), IgG: 3430 mg/dl (reference value 861 - 1747 mg/dl), and IgG4: 3140 mg/dl (reference value 11 - 121 mg/dl) were observed. Other laboratory data showed within normal ranges. The cervical tumor was diagnosed as Warthin’s tumor by the findings of fine-needle aspiration cytology and biopsy examination. Immunohistochemistry revealed numerous IgG4- and IgG-positive cells with fibrosis surrounding the epithelial component of Warthin’s tumor, suggesting IgG4-rerated sialadenitis. Finally, we diagnosed the cervical tumor as Warthin tumor with IgG4-related sialadenitis. This is the second report describing a case of Warthin’s tumor with possible involvement of IgG4-related sialadenitis.展开更多
This paper is concerned with the following fourth-order three-point boundary value problem , where , we discuss the existence of positive solutions to the above problem by applying to the fixed point theory in cones a...This paper is concerned with the following fourth-order three-point boundary value problem , where , we discuss the existence of positive solutions to the above problem by applying to the fixed point theory in cones and iterative technique.展开更多
The possible exotic nuclear properties in the neutron-rich Ca,Ni,Zr,and Sn isotopes are examined with the continuum Skyrme Hartree-Fock-Bogoliubov theory in the framework of the Green’s function method.The pairing co...The possible exotic nuclear properties in the neutron-rich Ca,Ni,Zr,and Sn isotopes are examined with the continuum Skyrme Hartree-Fock-Bogoliubov theory in the framework of the Green’s function method.The pairing correlation,the couplings with the continuum,and the blocking effects for the unpaired nucleon in odd-A nuclei are properly treated.The Skyrme interaction SLy4 is adopted for the ph channel and the density-dependentinteraction is adopted for the pp chan-nel,which well reproduce the experimental two-neutron separation energies S_(2n)and one-neutron separation energies Sn.It is found that the criterion S_(n)>0 predicts a neutron drip line with neutron numbers much smaller than those for S_(2n)>0.Owing to the unpaired odd neutron,the neutron pairing energies−E_(pair)in odd-A nuclei are much lower than those in the neighbor-ing even-even nuclei.By investigating the single-particle structures,the possible halo structures in the neutron-rich Ca,Ni,and Sn isotopes are predicted,where sharp increases in the root-mean-square(rms)radii with significant deviations from the traditional rA^(1∕3)rule and diffuse spatial density distributions are observed.Analyzing the contributions of various partial waves to the total neutron densityρlj(r)∕ρ(r)reveals that the orbitals located around the Fermi surface-particularly those with small angular momenta-significantly affect the extended nuclear density and large rms radii.The number of neutrons Nλ(N_(0))occupying above the Fermi surfacen(continuum threshold)is discussed,whose evolution as a function of the mass number A in each isotope is consistent with that of the pairing energy,supporting the key role of the pairing correlation in halo phenomena.展开更多
The pointwise space-time behaviors of the Green’s function and the global solution to the Vlasov-Poisson-Fokker-Planck(VPFP)system in three dimensional space are studied in this paper.It is shown that the Green’s fu...The pointwise space-time behaviors of the Green’s function and the global solution to the Vlasov-Poisson-Fokker-Planck(VPFP)system in three dimensional space are studied in this paper.It is shown that the Green’s function consists of the diffusion waves decaying exponentially in time but algebraically in space,and the singular kinetic waves which become smooth for all(t,x,v)when t>0.Furthermore,we establish the pointwise space-time behaviors of the global solution to the nonlinear VPFP system when the initial data is not necessarily smooth in terms of the Green’s function.展开更多
In this paper,we obtain Green’s functions of two-dimensional(2D)piezoelectric quasicrystal(PQC)in half-space and bimaterials.Based on the elastic theory of QCs,the Stroh formalism is used to derive the general soluti...In this paper,we obtain Green’s functions of two-dimensional(2D)piezoelectric quasicrystal(PQC)in half-space and bimaterials.Based on the elastic theory of QCs,the Stroh formalism is used to derive the general solutions of displacements and stresses.Then,we obtain the analytical solutions of half-space and bimaterial Green’s functions.Besides,the interfacial Green’s function for bimaterials is also obtained in the analytical form.Before numerical studies,a comparative study is carried out to validate the present solutions.Typical numerical examples are performed to investigate the effects of multi-physics loadings such as the line force,the line dislocation,the line charge,and the phason line force.As a result,the coupling effect among the phonon field,the phason field,and the electric field is prominent,and the butterfly-shaped contours are characteristic in 2D PQCs.In addition,the changes of material parameters cause variations in physical quantities to a certain degree.展开更多
This review deals with the nonequilibrium Green's function (NEGF) method applied to the problems of energy transport due to atomic vibrations (phonons), primarily for small jtmction systems. We present a pedagogi...This review deals with the nonequilibrium Green's function (NEGF) method applied to the problems of energy transport due to atomic vibrations (phonons), primarily for small jtmction systems. We present a pedagogical introduction to the subject, deriving some of the well-known results such as the Laudauer-like formula for heat current in ballistic systerms. The main aim of the review is to build the machinery of the method so that it can be applied to other situations, which are not directly treated here. In addition to the above, we consider a nmnber of applications of NEGF, not in routine model system calculations, but in a few new aspects showing the power and usefulness of the formalism. In partkaflar, we discuss the problems of multiple leads, coupled left-right-lead system, and system without a center. We also apply the method to the problem of full counting statisties. In the case of nonlinear svstems, we make general comments on the thermal expansion effect. phonon relaxation timv. and a certain class of mean-field approximations. Lastly, we examine the relationship between NEGF. reduced density matrix, and master equation approaches to thermal transport,展开更多
By using integral transform methods, the Green(s functions of horizontal harmonic force applied at the interior of the saturated half-space soil are obtained in the paper. The general solutions of the Biot dynamic equ...By using integral transform methods, the Green(s functions of horizontal harmonic force applied at the interior of the saturated half-space soil are obtained in the paper. The general solutions of the Biot dynamic equations in frequency domain are established through the use of Hankel integral transforms technique. Utilizing the above- mentioned general solutions, and the boundary conditions of the surface of the half-space and the continuous conditions at the plane of the horizontal force, the solutions of the boundary value problem can be determined. By the numerical inverse Hankel transforms method, the Green(s functions of the harmonic horizontal force are obtainable. The degenerate case of the results deduced from this paper agrees well with the known results. Two numerical examples are given in the paper.展开更多
The singularities, oscillatory performances and the contributing factors to the 3-'D translating-pulsating source Green function of deep-water Havelock form which consists of a local disturbance part and a far-field ...The singularities, oscillatory performances and the contributing factors to the 3-'D translating-pulsating source Green function of deep-water Havelock form which consists of a local disturbance part and a far-field wave-like part, are analyzed systematically. Relative numerical integral methods about the two parts are presented in this paper. An improved method based on LOBATTO rule is used to eliminate singularities caused respectively by infinite discontinuity and jump discontinuous node from the local disturbance part function, which makes the improvement of calculation efficiency and accuracy possible. And variable substitution is applied to remove the singularity existing at the end of the integral interval of the far-field wave-like part function. Two auxiliary techniques such as valid interval calculation and local refinement of integral steps technique in narrow zones near false singularities are applied so as to avoid unnecessary integration of invalid interval and improve integral accordance. Numerical test results have proved the efficiency and accuracy in these integral methods that thus can be applied to calculate hydrodynamic performance of floating structures moving in waves.展开更多
Based on one type of practical Biot's equation and the dynamic-stiffness matrices ofa poroelastic soil layer and half-space, Green's functions were derived for unitformly distributed loads acting on an inclined line...Based on one type of practical Biot's equation and the dynamic-stiffness matrices ofa poroelastic soil layer and half-space, Green's functions were derived for unitformly distributed loads acting on an inclined line in a poroelastie layered site. This analysis overcomes significant problems in wave scattering due to local soil conditions and dynamic soil-structure interaction. The Green's functions can be reduced to the case of an elastic layered site developed by Wolf in 1985. Parametric studies are then carried out through two example problems.展开更多
In this paper, we will introduce how to apply Green's function method to get the pointwise estimates for the solutions of Cauchy problem of nonlinear evolution equations with dissipative structure. First of all, we i...In this paper, we will introduce how to apply Green's function method to get the pointwise estimates for the solutions of Cauchy problem of nonlinear evolution equations with dissipative structure. First of all, we introduce the pointwise estimates of the time-asymptotic shape of the solutions of the isentropic Navier-Stokes equations and show to exhibit the generalized Huygen's principle. Then, for other nonlinear dissipative evolution equations, we will only introduce the result and give some brief explanations. Our approach is based on the detailed analysis of the Green's function of the linearized system and micro-local analysis, such as frequency decomposition and so on.展开更多
In this paper, we consider the existence of positive solutions of second-order periodic boundary value problem where 0 〈 ε 〈 1/2, g : [0, 2π] →R is continuous, f : [0, ∞) →R is continuous and λ 〉 0 is a pa...In this paper, we consider the existence of positive solutions of second-order periodic boundary value problem where 0 〈 ε 〈 1/2, g : [0, 2π] →R is continuous, f : [0, ∞) →R is continuous and λ 〉 0 is a parameter.展开更多
This study proposes a Green's function, an essential representation of water-saturated ground under moving excitation, to simulate ground borne vibration from trains. First, general solutions to the governing equatio...This study proposes a Green's function, an essential representation of water-saturated ground under moving excitation, to simulate ground borne vibration from trains. First, general solutions to the governing equations of poroelastic medium are derived by means of integral transform. Secondly, the transmission and reflection matrix approach is used to formulate the relationship between displacement and stress of the stratified ground, which results in the matrix of the Green's function. Then the Green's function is combined into a train-track-ground model, and is verified by typical examples and a field test. Additional simulations show that the computed ground vibration attenuates faster in the immediate vicinity of the track than in the surrounding area. The wavelength of wheel-rail unevenness has a notable effect on computed displacement and pore pressure. The variation of vibration intensity with the depth of ground is significantly influenced by the layering of the strata soil. When the train speed is equal to the velocity of the Rayleigh wave, the Mach cone appears in the simulated wave field. The proposed Green's function is an appropriate representation for a layered ground with shallow ground water table, and will be helpful to understand the dynamic responses of the ground to complicated moving excitation.展开更多
Green's functions for Blot's dynamic equation in the frequency domain can be a highly useful tool for the investigation of dynamic responses of a saturated porous medium. Its applications are found in soil dynamics,...Green's functions for Blot's dynamic equation in the frequency domain can be a highly useful tool for the investigation of dynamic responses of a saturated porous medium. Its applications are found in soil dynamics, seismology, earthquake engineering, rock mechanics, geophysics, and acoustics. However, the mathematical work for deriving it can be daunting. Green's functions have been presented utilizing an analogy between the dynamic thermoelasticity and the dynamic poroelasticity in the frequency domain using the u-p formulation. In this work, a special term "decoupling coefficient" for the decomposition of the fast and slow dilatational waves is proposed and expressed to present a new methodology for deriving the poroelastodynamic Green's functions. The correct- ness of the solution is demonstrated by numerically comparing the current solution with Cheng's previous solution. The separation of the two waves in the present methodology allows the more accurate evaluation of Green's functions, particularly the solution of the slow dilatational wave. This can be advantageous for the numerical implementation of the boundary element method (BEM) and other applications.展开更多
The dynamic stiffness method combined with the Fourier transform is utilized to derive the in-plane Green’s functions for inclined and uniformly distributed loads in a multi-layered transversely isotropic(TI)half-s...The dynamic stiffness method combined with the Fourier transform is utilized to derive the in-plane Green’s functions for inclined and uniformly distributed loads in a multi-layered transversely isotropic(TI)half-space.The loaded layer is fixed to obtain solutions restricted in it and the corresponding reactions forces,which are then applied to the total system with the opposite sign.By adding solutions restricted in the loaded layer to solutions from the reaction forces,the global solutions in the wavenumber domain are obtained,and the dynamic Green’s functions in the space domain are recovered by the inverse Fourier transform.The presented formulations can be reduced to the isotropic case developed by Wolf(1985),and are further verified by comparisons with existing solutions in a uniform isotropic as well as a layered TI halfspace subjected to horizontally distributed loads which are special cases of the more general problem addressed.The deduced Green’s functions,in conjunction with boundary element methods,will lead to significant advances in the investigation of a variety of wave scattering,wave radiation and soil-structure interaction problems in a layered TI site.Selected numerical results are given to investigate the influence of material anisotropy,frequency of excitation,inclination angle and layered on the responses of displacement and stress,and some conclusions are drawn.展开更多
基金financial support from the National Natural Science Foundation of China(11572119)
文摘Because most piezoelectric devices have interfaces with fluid in engineering, it is valuable to study the coupled field between fluid and piezoelectric media. As the fundamental problem, the 3D Green's functions for point forces and point charge loaded in the fluid and piezoelectric bimaterials are studied in this paper. Based on the 3D general solutions expressed by harmonic functions, we constructed the suitable harmonic functions with undetermined constants at first. Then, the couple field in the fluid and piezoelectric bimaterials can be derived by substitution of harmonic functions into general solutions. These constants can be obtained by virtue of the compatibility, boundary, and equilibrium conditions. At last, the characteristics of the electromechanical coupled fields are shown by numerical results.
基金supported by National Natural Science Foundation of China (Grants No.41374056)the Fundamental Research Funds for the Central Universities (WK2080000053)
文摘With dense seismic arrays and advanced imaging methods, regional three-dimensional (3D) Earth models have become more accurate. It is now increasingly feasible and advantageous to use a 3D Earth model to better locate earthquakes and invert their source mechanisms by fitting synthetics to observed waveforms. In this study, we develop an approach to determine both the earthquake location and source mechanism from waveform information. The observed waveforms are filtered in different frequency bands and separated into windows for the individual phases. Instead of picking the arrival times, the traveltime differences are measured by cross-correlation between synthetic waveforms based on the 3D Earth model and observed waveforms. The earthquake location is determined by minimizing the cross-correlation traveltime differences. We then fix the horizontal location of the earthquake and perform a grid search in depth to determine the source mechanism at each point by fitting the synthetic and observed waveforms. This new method is verified by a synthetic test with noise added to the synthetic waveforms and a realistic station distribution. We apply this method to a series of Mw3.4-5.6 earthquakes in the Longmenshan fault (LMSF) zone, a region with rugged topography between the eastern margin of the Tibetan plateau and the western part of the Sichuan basin. The results show that our solutions result in improved waveform fits compared to the source parameters from the catalogs we used and the location can be better constrained than the amplitude-only approach. Furthermore, the source solutions with realistic topography provide a better fit to the observed waveforms than those without the topography, indicating the need to take the topography into account in regions with rugged topography.
基金Supported by Hunan Provincial Social Science Fund Project(21YBX021)Hunan Provincial Natural Science Foundation Project(2024JJ7234).
文摘Since the 18 th National Congress of the Communist Party of China,General Secretary Xi Jinping delivered a series of speeches on ecological environment and poverty governance,forming the Xi Jinping s eco-poverty alleviation ideology.In this paper,the Xi Jinping s eco-poverty alleviation ideology is taken as the research object.Using the methods of literature analysis and comparative analysis,the origin of eco-poverty alleviation theory is explored from the common prosperity theory and the theory of ecological capital,and the practice foundation is found out from practical cases.The relationship between the ecological damage and poverty is systematically analyzed,and the mechanism of ecological poverty is explored in detail.The basic connotation of Xi Jinping s eco-poverty alleviation is expounded,and it consists of three parts:guiding ideology layer,implementation layer,and guarantee layer.By perfecting and innovating the market mechanism,social management mechanism,performance evaluation mechanism,integration mechanism with other poverty alleviation methods,and ecological immigration mechanism of ecological poverty,the realization of Xi Jinping s eco-poverty alleviation concept could be guaranteed.
文摘Warthin’s tumor is the second most frequent neoplasm next to pleomorphic adenoma in the salivary gland. The tumor contains the epithelial oncocyte cells with the presence of rich-mitochondria and their surrounding abundant lymphocytes. A relatively new disease entity of IgG4-related disease frequently occurs in the salivary gland. However, the coexistence of Warthin’s tumor and IgG4-related disease is scarcely observed. We have recently experienced a rare case of Warthin’s tumor with IgG4-related sialadenitis. A 51-year-old man presented to our hospital, complaining of a mass with right submandibular tenderness and spontaneous pain. A computed tomography scan of the cervical region revealed a suspicion of lymph node proliferative disease, including malignant lymphoma. Elevated serum levels of IL-2R: 1843 U/ml (reference value 122 - 496 U/ml), IgG: 3430 mg/dl (reference value 861 - 1747 mg/dl), and IgG4: 3140 mg/dl (reference value 11 - 121 mg/dl) were observed. Other laboratory data showed within normal ranges. The cervical tumor was diagnosed as Warthin’s tumor by the findings of fine-needle aspiration cytology and biopsy examination. Immunohistochemistry revealed numerous IgG4- and IgG-positive cells with fibrosis surrounding the epithelial component of Warthin’s tumor, suggesting IgG4-rerated sialadenitis. Finally, we diagnosed the cervical tumor as Warthin tumor with IgG4-related sialadenitis. This is the second report describing a case of Warthin’s tumor with possible involvement of IgG4-related sialadenitis.
文摘This paper is concerned with the following fourth-order three-point boundary value problem , where , we discuss the existence of positive solutions to the above problem by applying to the fixed point theory in cones and iterative technique.
基金the National Natural Science Foundation of China(No.U2032141)the Open Project of Guangxi Key Laboratory of Nuclear Physics and Nuclear Technology(No.NLK2022-02)+4 种基金the Central Government Guidance Funds for Local Scientific and Technological Development,China(Guike ZY22096024)the Natural Science Foundation of Henan Province(No.202300410479)the Guizhou Provincial Science and Technology Projects(No.ZK[2022]203)the Foundation of Fundamental Research for Young Teachers of Zhengzhou University(No.JC202041041)the Physics Research and Development Program of Zhengzhou University(No.32410217).
文摘The possible exotic nuclear properties in the neutron-rich Ca,Ni,Zr,and Sn isotopes are examined with the continuum Skyrme Hartree-Fock-Bogoliubov theory in the framework of the Green’s function method.The pairing correlation,the couplings with the continuum,and the blocking effects for the unpaired nucleon in odd-A nuclei are properly treated.The Skyrme interaction SLy4 is adopted for the ph channel and the density-dependentinteraction is adopted for the pp chan-nel,which well reproduce the experimental two-neutron separation energies S_(2n)and one-neutron separation energies Sn.It is found that the criterion S_(n)>0 predicts a neutron drip line with neutron numbers much smaller than those for S_(2n)>0.Owing to the unpaired odd neutron,the neutron pairing energies−E_(pair)in odd-A nuclei are much lower than those in the neighbor-ing even-even nuclei.By investigating the single-particle structures,the possible halo structures in the neutron-rich Ca,Ni,and Sn isotopes are predicted,where sharp increases in the root-mean-square(rms)radii with significant deviations from the traditional rA^(1∕3)rule and diffuse spatial density distributions are observed.Analyzing the contributions of various partial waves to the total neutron densityρlj(r)∕ρ(r)reveals that the orbitals located around the Fermi surface-particularly those with small angular momenta-significantly affect the extended nuclear density and large rms radii.The number of neutrons Nλ(N_(0))occupying above the Fermi surfacen(continuum threshold)is discussed,whose evolution as a function of the mass number A in each isotope is consistent with that of the pairing energy,supporting the key role of the pairing correlation in halo phenomena.
基金supported by National Natural Science Foundation of China(11671100 and 12171104)the National Science Fund for Excellent Young Scholars(11922107)Guangxi Natural Science Foundation(2018GXNSFAA138210 and 2019JJG110010)。
文摘The pointwise space-time behaviors of the Green’s function and the global solution to the Vlasov-Poisson-Fokker-Planck(VPFP)system in three dimensional space are studied in this paper.It is shown that the Green’s function consists of the diffusion waves decaying exponentially in time but algebraically in space,and the singular kinetic waves which become smooth for all(t,x,v)when t>0.Furthermore,we establish the pointwise space-time behaviors of the global solution to the nonlinear VPFP system when the initial data is not necessarily smooth in terms of the Green’s function.
基金the National Natural Science Foundation of China(Nos.11972365 and 12102458)。
文摘In this paper,we obtain Green’s functions of two-dimensional(2D)piezoelectric quasicrystal(PQC)in half-space and bimaterials.Based on the elastic theory of QCs,the Stroh formalism is used to derive the general solutions of displacements and stresses.Then,we obtain the analytical solutions of half-space and bimaterial Green’s functions.Besides,the interfacial Green’s function for bimaterials is also obtained in the analytical form.Before numerical studies,a comparative study is carried out to validate the present solutions.Typical numerical examples are performed to investigate the effects of multi-physics loadings such as the line force,the line dislocation,the line charge,and the phason line force.As a result,the coupling effect among the phonon field,the phason field,and the electric field is prominent,and the butterfly-shaped contours are characteristic in 2D PQCs.In addition,the changes of material parameters cause variations in physical quantities to a certain degree.
文摘This review deals with the nonequilibrium Green's function (NEGF) method applied to the problems of energy transport due to atomic vibrations (phonons), primarily for small jtmction systems. We present a pedagogical introduction to the subject, deriving some of the well-known results such as the Laudauer-like formula for heat current in ballistic systerms. The main aim of the review is to build the machinery of the method so that it can be applied to other situations, which are not directly treated here. In addition to the above, we consider a nmnber of applications of NEGF, not in routine model system calculations, but in a few new aspects showing the power and usefulness of the formalism. In partkaflar, we discuss the problems of multiple leads, coupled left-right-lead system, and system without a center. We also apply the method to the problem of full counting statisties. In the case of nonlinear svstems, we make general comments on the thermal expansion effect. phonon relaxation timv. and a certain class of mean-field approximations. Lastly, we examine the relationship between NEGF. reduced density matrix, and master equation approaches to thermal transport,
基金State Natural Science Foundation (59879012) and Doctoral Foundation from State Education Commission (98024832).
文摘By using integral transform methods, the Green(s functions of horizontal harmonic force applied at the interior of the saturated half-space soil are obtained in the paper. The general solutions of the Biot dynamic equations in frequency domain are established through the use of Hankel integral transforms technique. Utilizing the above- mentioned general solutions, and the boundary conditions of the surface of the half-space and the continuous conditions at the plane of the horizontal force, the solutions of the boundary value problem can be determined. By the numerical inverse Hankel transforms method, the Green(s functions of the harmonic horizontal force are obtainable. The degenerate case of the results deduced from this paper agrees well with the known results. Two numerical examples are given in the paper.
基金supported by the National Natural Science Foundation of China (Grant No. 50879090)
文摘The singularities, oscillatory performances and the contributing factors to the 3-'D translating-pulsating source Green function of deep-water Havelock form which consists of a local disturbance part and a far-field wave-like part, are analyzed systematically. Relative numerical integral methods about the two parts are presented in this paper. An improved method based on LOBATTO rule is used to eliminate singularities caused respectively by infinite discontinuity and jump discontinuous node from the local disturbance part function, which makes the improvement of calculation efficiency and accuracy possible. And variable substitution is applied to remove the singularity existing at the end of the integral interval of the far-field wave-like part function. Two auxiliary techniques such as valid interval calculation and local refinement of integral steps technique in narrow zones near false singularities are applied so as to avoid unnecessary integration of invalid interval and improve integral accordance. Numerical test results have proved the efficiency and accuracy in these integral methods that thus can be applied to calculate hydrodynamic performance of floating structures moving in waves.
基金National Natural Science Foundation of China Under Grant No.50378063
文摘Based on one type of practical Biot's equation and the dynamic-stiffness matrices ofa poroelastic soil layer and half-space, Green's functions were derived for unitformly distributed loads acting on an inclined line in a poroelastie layered site. This analysis overcomes significant problems in wave scattering due to local soil conditions and dynamic soil-structure interaction. The Green's functions can be reduced to the case of an elastic layered site developed by Wolf in 1985. Parametric studies are then carried out through two example problems.
基金supported by National Science Foundation of China(11071162)Shanghai Municipal Natural Science Foundation (09ZR1413500)
文摘In this paper, we will introduce how to apply Green's function method to get the pointwise estimates for the solutions of Cauchy problem of nonlinear evolution equations with dissipative structure. First of all, we introduce the pointwise estimates of the time-asymptotic shape of the solutions of the isentropic Navier-Stokes equations and show to exhibit the generalized Huygen's principle. Then, for other nonlinear dissipative evolution equations, we will only introduce the result and give some brief explanations. Our approach is based on the detailed analysis of the Green's function of the linearized system and micro-local analysis, such as frequency decomposition and so on.
基金Supported by the National Natural Science Foundation of China(No.11321627,11401479,71561024,11561063)China Postdoctoral Science Foundation(2014M562472)+1 种基金Postdoctoral Science Foundation of Gansu Provincethe Science Research Project for Colleges and Universities of Gansu Province(2016A-003)
文摘In this paper, we consider the existence of positive solutions of second-order periodic boundary value problem where 0 〈 ε 〈 1/2, g : [0, 2π] →R is continuous, f : [0, ∞) →R is continuous and λ 〉 0 is a parameter.
基金National Natural Science Foundation of China Key Project,under Grant No.50538030Postdoctoral Science Foundation of China under Grant No.2013M531084Natural Science Foundation of Heilongjiang Province of China under Grant No.E201221
文摘This study proposes a Green's function, an essential representation of water-saturated ground under moving excitation, to simulate ground borne vibration from trains. First, general solutions to the governing equations of poroelastic medium are derived by means of integral transform. Secondly, the transmission and reflection matrix approach is used to formulate the relationship between displacement and stress of the stratified ground, which results in the matrix of the Green's function. Then the Green's function is combined into a train-track-ground model, and is verified by typical examples and a field test. Additional simulations show that the computed ground vibration attenuates faster in the immediate vicinity of the track than in the surrounding area. The wavelength of wheel-rail unevenness has a notable effect on computed displacement and pore pressure. The variation of vibration intensity with the depth of ground is significantly influenced by the layering of the strata soil. When the train speed is equal to the velocity of the Rayleigh wave, the Mach cone appears in the simulated wave field. The proposed Green's function is an appropriate representation for a layered ground with shallow ground water table, and will be helpful to understand the dynamic responses of the ground to complicated moving excitation.
基金Project supported by the National Natural Science Foundation of China(Nos.51478435,11402150,and 11172268)
文摘Green's functions for Blot's dynamic equation in the frequency domain can be a highly useful tool for the investigation of dynamic responses of a saturated porous medium. Its applications are found in soil dynamics, seismology, earthquake engineering, rock mechanics, geophysics, and acoustics. However, the mathematical work for deriving it can be daunting. Green's functions have been presented utilizing an analogy between the dynamic thermoelasticity and the dynamic poroelasticity in the frequency domain using the u-p formulation. In this work, a special term "decoupling coefficient" for the decomposition of the fast and slow dilatational waves is proposed and expressed to present a new methodology for deriving the poroelastodynamic Green's functions. The correct- ness of the solution is demonstrated by numerically comparing the current solution with Cheng's previous solution. The separation of the two waves in the present methodology allows the more accurate evaluation of Green's functions, particularly the solution of the slow dilatational wave. This can be advantageous for the numerical implementation of the boundary element method (BEM) and other applications.
基金National Natural Science Foundation of China under grant No.51578373 and 51578372the Natural Science Foundation of Tianjin Municipality under Grant No.16JCYBJC21600
文摘The dynamic stiffness method combined with the Fourier transform is utilized to derive the in-plane Green’s functions for inclined and uniformly distributed loads in a multi-layered transversely isotropic(TI)half-space.The loaded layer is fixed to obtain solutions restricted in it and the corresponding reactions forces,which are then applied to the total system with the opposite sign.By adding solutions restricted in the loaded layer to solutions from the reaction forces,the global solutions in the wavenumber domain are obtained,and the dynamic Green’s functions in the space domain are recovered by the inverse Fourier transform.The presented formulations can be reduced to the isotropic case developed by Wolf(1985),and are further verified by comparisons with existing solutions in a uniform isotropic as well as a layered TI halfspace subjected to horizontally distributed loads which are special cases of the more general problem addressed.The deduced Green’s functions,in conjunction with boundary element methods,will lead to significant advances in the investigation of a variety of wave scattering,wave radiation and soil-structure interaction problems in a layered TI site.Selected numerical results are given to investigate the influence of material anisotropy,frequency of excitation,inclination angle and layered on the responses of displacement and stress,and some conclusions are drawn.