This paper studies the symmetry, with respect to the real axis, of the point spectrum of the upper triangular infinite dimensional Hamiltonian operator H. Note that the point spectrum of H can be described as σp（H）...This paper studies the symmetry, with respect to the real axis, of the point spectrum of the upper triangular infinite dimensional Hamiltonian operator H. Note that the point spectrum of H can be described as σp（H） = σp （A） U σp1 （-A＊）. Using the characteristic of the set σp1（-A＊）, we divide the point spectrum σp （d） of A into three disjoint parts. Then, a necessary and sufficient condition is obtained under which σp1（-A＊） and one part of σp（A） are symmetric with respect to the real axis each other. Based on this result, the symmetry of σp（H） is completely given. Moreover, the above result is applied to thin plates on elastic foundation, plane elasticity problems and harmonic equations.展开更多
In this paper,by using characterization of the point spectrum of the upper triangular infinite dimensional Hamiltonian operator H,a necessary and sufficient condition is obtained on the symmetry of σp(A) and σp1(-A*...In this paper,by using characterization of the point spectrum of the upper triangular infinite dimensional Hamiltonian operator H,a necessary and sufficient condition is obtained on the symmetry of σp(A) and σp1(-A*) with respect to the imaginary axis.Then the symmetry of the point spectrum of H is given,and several examples are presented to illustrate the results.展开更多
It is well known that the sea return echo contains contributions from at least two scattering mechanisms. In addition to the resonant Bragg scattering, the specular point scattering plays an important role as the inci...It is well known that the sea return echo contains contributions from at least two scattering mechanisms. In addition to the resonant Bragg scattering, the specular point scattering plays an important role as the incidence angle becomes smaller （≥ 20°）. Here, in combination with the Kirchhoff integral equation of scattering field and the stationary phase approximation, analytical expressions for Doppler shift and spectral bandwidth of specular point scattering, which are insensitive to the polarization state, are derived theoretically. For comparison, the simulated results related to the two-scale method （TSM） and the method of moment （MOM） are also presented. It is found that the Doppler shift and the spectral bandwidth given by TSM are insufficient at small incidence angles. However, a comparison between the analytical results and the numerical simulations by MOM in the backscatter configuration shows that our proposed formulas are valid for the specular point scattering case. In this work, the dependences of the predicted results on incidence angle, radar frequency, and wind speed are also discussed. The obtained conclusions seem promising for a better understanding of the Doppler spectra of the specular point scattering fields from time-varying sea surfaces.展开更多
基金Supported by the National Natural Science Foundation of China (No. 11061019, 10962004, 11101200)the Chunhui Program of Ministry of Education of China (No. Z2009-1-01010)+1 种基金the Natural Science Foundation of Inner Mongolia (No. 2010MS0110, 2009BS0101)the Cultivation of Innovative Talent of ‘211 Project’ of Inner Mongolia University
文摘This paper studies the symmetry, with respect to the real axis, of the point spectrum of the upper triangular infinite dimensional Hamiltonian operator H. Note that the point spectrum of H can be described as σp（H） = σp （A） U σp1 （-A＊）. Using the characteristic of the set σp1（-A＊）, we divide the point spectrum σp （d） of A into three disjoint parts. Then, a necessary and sufficient condition is obtained under which σp1（-A＊） and one part of σp（A） are symmetric with respect to the real axis each other. Based on this result, the symmetry of σp（H） is completely given. Moreover, the above result is applied to thin plates on elastic foundation, plane elasticity problems and harmonic equations.
基金Foundation item： the National Natural Science Foundation of China （No. 10562002） the Natural Science Foundation of Inner Mongolia （Nos. 200508010103+2 种基金 200711020106） the Specialized Research Fund of the Doctoral Program of Higher Education of China （No. 20070126002） Research Foundation for Talented Scholars of Inner Mongolia University （No. 206029）.
文摘In this paper,by using characterization of the point spectrum of the upper triangular infinite dimensional Hamiltonian operator H,a necessary and sufficient condition is obtained on the symmetry of σp(A) and σp1(-A*) with respect to the imaginary axis.Then the symmetry of the point spectrum of H is given,and several examples are presented to illustrate the results.
基金Project supported by the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.40906088)the Specialized Research Fund for the Doctoral Program of Higher Education,China(Grant No.200804231021)
文摘It is well known that the sea return echo contains contributions from at least two scattering mechanisms. In addition to the resonant Bragg scattering, the specular point scattering plays an important role as the incidence angle becomes smaller （≥ 20°）. Here, in combination with the Kirchhoff integral equation of scattering field and the stationary phase approximation, analytical expressions for Doppler shift and spectral bandwidth of specular point scattering, which are insensitive to the polarization state, are derived theoretically. For comparison, the simulated results related to the two-scale method （TSM） and the method of moment （MOM） are also presented. It is found that the Doppler shift and the spectral bandwidth given by TSM are insufficient at small incidence angles. However, a comparison between the analytical results and the numerical simulations by MOM in the backscatter configuration shows that our proposed formulas are valid for the specular point scattering case. In this work, the dependences of the predicted results on incidence angle, radar frequency, and wind speed are also discussed. The obtained conclusions seem promising for a better understanding of the Doppler spectra of the specular point scattering fields from time-varying sea surfaces.
