Based on FDTD difference expressions and eigenfunctions of Maxwell functions in cylindrical coordinates, mesh wave impedances (MWIs) in 2D and 3D cylindrical coordinates were introduced. Combined with the concept of p...Based on FDTD difference expressions and eigenfunctions of Maxwell functions in cylindrical coordinates, mesh wave impedances (MWIs) in 2D and 3D cylindrical coordinates were introduced. Combined with the concept of perfectly matched layer (PML), MWI PML absorbing boundary condition (ABC) algorithm was deduced in 2D cylindrical coordinates. Numerical experiments were done to investigate the validity of MWI and its application in cylindrical coordinates FDTD algorithm. The results showed that MWI in cylindrical coordinates can be used to accurately calculate the numerical reflection error caused by different mesh increments in non uniform FDTD. MWI can also provide theoretical criterion to define the permitted variable range of mesh dimension. MWI PML ABC is easy to be applied and reduces low numerical reflection, which only causes a little higher reflection error compared with Teixeira's PML.展开更多
Electromagnetic bandgap （EBG） materials are periodic structures capable of prohibiting the propagation of electromagnetic waves within a certain band of frequencies. This characteristic of EBG has wide application. ...Electromagnetic bandgap （EBG） materials are periodic structures capable of prohibiting the propagation of electromagnetic waves within a certain band of frequencies. This characteristic of EBG has wide application. The structures to be studied here are mainly planar EBG materials of two dimensions, which are periodic arrays of holes etched in the ground plane of a conventional microstrip line. EBG structures are calculated with finite-difference time-domain （FDTD） method in this paper. Technique of the perfectly matched layer is used for the absorption of electromagnetic waves in FDTD. The FDTD method is programmed with the blend of C++ and Matlab languages, which makes the program both simple and fast computing. A kind of new EBG structure is brought out through a lot of experiments and analyses. A filter with wide stop-band and another filter with two stop-bands are designed.展开更多
In the paper, necessary and sufficient conditions are provided for a function involving the divided difference of two psi functions to be completely monotonic. Consequently, a class of inequalities for sums are presen...In the paper, necessary and sufficient conditions are provided for a function involving the divided difference of two psi functions to be completely monotonic. Consequently, a class of inequalities for sums are presented, the logarithmically complete monotonicity of a function involving the ratio of two gamma functions are derived, and two double inequalities for bounding the ratio of two gamma functions are discovered.展开更多
文摘Based on FDTD difference expressions and eigenfunctions of Maxwell functions in cylindrical coordinates, mesh wave impedances (MWIs) in 2D and 3D cylindrical coordinates were introduced. Combined with the concept of perfectly matched layer (PML), MWI PML absorbing boundary condition (ABC) algorithm was deduced in 2D cylindrical coordinates. Numerical experiments were done to investigate the validity of MWI and its application in cylindrical coordinates FDTD algorithm. The results showed that MWI in cylindrical coordinates can be used to accurately calculate the numerical reflection error caused by different mesh increments in non uniform FDTD. MWI can also provide theoretical criterion to define the permitted variable range of mesh dimension. MWI PML ABC is easy to be applied and reduces low numerical reflection, which only causes a little higher reflection error compared with Teixeira's PML.
文摘Electromagnetic bandgap （EBG） materials are periodic structures capable of prohibiting the propagation of electromagnetic waves within a certain band of frequencies. This characteristic of EBG has wide application. The structures to be studied here are mainly planar EBG materials of two dimensions, which are periodic arrays of holes etched in the ground plane of a conventional microstrip line. EBG structures are calculated with finite-difference time-domain （FDTD） method in this paper. Technique of the perfectly matched layer is used for the absorption of electromagnetic waves in FDTD. The FDTD method is programmed with the blend of C++ and Matlab languages, which makes the program both simple and fast computing. A kind of new EBG structure is brought out through a lot of experiments and analyses. A filter with wide stop-band and another filter with two stop-bands are designed.
基金supported partially by the China Scholarship Council and the Science Foundation of Tianjin Polytechnic Universitysupported in part by the Natural Science Foundation Project of Chongqing,China(Grant No.CSTC2011JJA00024)+1 种基金the Research Project of Science and Technology of Chongqing Education Commission,China(Grant No.KJ120625)the Fund of Chongqing Normal University,China(Grant Nos.10XLR017 and 2011XLZ07)
文摘In the paper, necessary and sufficient conditions are provided for a function involving the divided difference of two psi functions to be completely monotonic. Consequently, a class of inequalities for sums are presented, the logarithmically complete monotonicity of a function involving the ratio of two gamma functions are derived, and two double inequalities for bounding the ratio of two gamma functions are discovered.
