Metallic ring-shaped nanotube arrays are proposed and its optical transmission properties are studied by using finite-difference time-domain （FDTD） method. Compared with the transmission spectra of conventional circ...Metallic ring-shaped nanotube arrays are proposed and its optical transmission properties are studied by using finite-difference time-domain （FDTD） method. Compared with the transmission spectra of conventional circular nanotube arrays, two photonic band gaps are emerged in the transmission spectra offing-shaped nanotube arrays, the two band gaps and transmission spectra are adjusted by the length, inner radius, intertube spacing and the dielectric constants of the core and embedding medium, and magnitude modification, redshift and blueshift of the resonance modes are observed. A metallic ring-shaped nanotube arrays for subwavelength band-stop filter in the range of visible light can be achieved. To understand its physical origin, field-interference mechanism was suggested by the field distributions. The proposed nanostructures and results may have great potential applications in subwavelength near-field optics.展开更多
Large calculation error can be formed by directly employing the conventional Yee’s grid to curve surfaces.In order to alleviate such condition,unconditionally stable CrankNicolson Douglas-Gunn(CNDG)algorithm with is ...Large calculation error can be formed by directly employing the conventional Yee’s grid to curve surfaces.In order to alleviate such condition,unconditionally stable CrankNicolson Douglas-Gunn(CNDG)algorithm with is proposed for rotationally symmetric multi-scale problems in anisotropic magnetized plasma.Within the CNDG algorithm,an alternative scheme for the simulation of anisotropic plasma is proposed in body-of-revolution domains.Convolutional perfectly matched layer(CPML)formulation is proposed to efficiently solve the open region problems.Numerical example is carried out for the illustration of effectiveness including the efficiency,resources,and absorption.Through the results,it can be concluded that the proposed scheme shows considerable performance during the simulation.展开更多
The absorbing boundary is the key in numerical simulation of borehole radar.Perfect match layer(PML) was chosen as the absorbing boundary in numerical simulation of GPR.But CPML(convolutional perfect match layer) appr...The absorbing boundary is the key in numerical simulation of borehole radar.Perfect match layer(PML) was chosen as the absorbing boundary in numerical simulation of GPR.But CPML(convolutional perfect match layer) approach that we have chosen has the advantage of being media independent.Beginning with the Maxwell equations in a two-dimensional structure,numerical formulas of finite-difference time-domain(FDTD) method with CPML boundary condition for transverse electric(TE) or transverse magnetic(TM) wave are presented in details.Also,there are three models for borehole-GPR simulation.By analyzing the simulation results,the features of targets in GPR are obtained,which can provide a better interpretation of real radar data.The results show that CPML is well suited for the simulation of borehole-GPR.展开更多
To efficiently simulate and calculate the radar cross section(RCS) related electromagnetic problems by employing the finite-difference time-domain(FDTD) algorithm, an efficient stretched coordinate perfectly matched l...To efficiently simulate and calculate the radar cross section(RCS) related electromagnetic problems by employing the finite-difference time-domain(FDTD) algorithm, an efficient stretched coordinate perfectly matched layer(ESC-PML) based upon the exponential time differencing(ETD) method is proposed.The proposed implementation can not only reduce the number of auxiliary variables in the SC-PML regions but also maintain the ability of the original SC-PML in terms of the absorbing performance. Compared with the other existed algorithms, the ETDFDTD method shows the least memory consumption resulting in the computational efficiency. The effectiveness and efficiency of the proposed ESC-PML scheme is verified through the RCS relevant problems including the perfect E conductor(PEC) sphere model and the patch antenna model. The results indicate that the proposed scheme has the advantages of the ETD-FDTD method and ESC-PML scheme in terms of high computational efficiency and considerable computational accuracy.展开更多
In order to simulate metamaterial rotational symmetric open region problems,unconditionally stable perfectly match layer(PML)implementation is proposed in the body of revolution(BOR)finite-difference time-domain(FDTD)...In order to simulate metamaterial rotational symmetric open region problems,unconditionally stable perfectly match layer(PML)implementation is proposed in the body of revolution(BOR)finite-difference time-domain(FDTD)lattice.More precisely,the proposed algorithm is implemented by the Crank-Nicolson(CN)Douglas-Gunn(DG)procedure for BOR metamaterial simulation.The constitutive relationship of metamaterial can be expressed by the Drude model and calculated by the piecewise linear recursive convolution(PLRC)approach.The effectiveness including absorption,efficiency,and accuracy is demonstrated through the numerical example.It can be concluded that the proposed implementation is to take the advantages of the CNDG-PML procedure,PLRC approach,and BORFDTD algorithm in terms of considerable accuracy,enhanced absorption and remarkable efficiency.Meanwhile,it can be demonstrated that the proposed scheme can maintain its unconditional stability when the time step exceeds the CourantFriedrichs-Levy(CFL)condition.展开更多
An unsplit-field higher order nearly perfectly matched layer(NPML)based on the auxiliary differential equation approach is introduced in three-dimensional finite-difference timedomain lattices.The proposed scheme has ...An unsplit-field higher order nearly perfectly matched layer(NPML)based on the auxiliary differential equation approach is introduced in three-dimensional finite-difference timedomain lattices.The proposed scheme has the advantage of both the NPML scheme and the higher order concept in terms of the improved absorbing performance and considerable computational efficiency.By incorporating with the generalized material independent concept,the proposed implementation is indepen dent of the material’s type.Thus,it has the advantages of terminating arbitrary media without changing the updated equations in the PML regions.Its effectiveness and efficiency is further demonstrated through numerical examples.展开更多
Because the conventional ultra wideband（UWB） radar imaging algorithm cannot meet the demand in the capability of multiple targets detection,a novel UWB radar imaging algorithm based on the near field radiation theor...Because the conventional ultra wideband（UWB） radar imaging algorithm cannot meet the demand in the capability of multiple targets detection,a novel UWB radar imaging algorithm based on the near field radiation theory of dipole is presented.On the foundation of researching the principle of a time domain imaging algorithm,the back projection（BP） algorithm is derived and analyzed.Firstly,the far field sampling data are transferred to the near field sampling data by using the near field radiation theory of dipole.Then the BP algorithm is applied to target detection.The capability of the new algorithm to detect the multi-target is verified by using the finite-difference time-domain method,and the threedimensional images of targets are obtained.The coupling effect between targets for imaging is analyzed.The simulation results show that the new UWB radar imaging algorithm based on the near field radiation theory of dipole could weaken the coupling effect for imaging,and as a result the quality of imaging is improved.展开更多
To handle the electromagnetic problems of the bi-static radar cross section （RCS） calculation of scatterer in a wide fre- quency band, a finite-difference time-domain （FDTD） extrapolation method combining with dis...To handle the electromagnetic problems of the bi-static radar cross section （RCS） calculation of scatterer in a wide fre- quency band, a finite-difference time-domain （FDTD） extrapolation method combining with discrete Fourier transform （DFT） is pro- posed. By comparing the formulas between the steady state field extrapolation method and the transient field extrapolation method, a novel extrapolation method combining with DFT used in FDTD is proposed when a transient field incident wave is introduced. With the proposed method, the full-angle RCS distribution in a wide fre- quency band can be achieved through one-time FDTD calculation. Afterwards, the back-scattering RCS distributions of a double olive body and a sphere-cone body are calculated. Numerical results verify the validity of the proposed method.展开更多
基金Projects(11164007,61275174)supported by the National Natural Science Foundation of ChinaProject(20100162110068)supported by the Doctoral Program of Higher Education of China+1 种基金Project(20132BAB212007)supported by the Natural Science Foundation of Jiangxi Province,ChinaProject(GJJ11107)supported by Scientific Foundation of Jiangxi Education Department,China
文摘Metallic ring-shaped nanotube arrays are proposed and its optical transmission properties are studied by using finite-difference time-domain （FDTD） method. Compared with the transmission spectra of conventional circular nanotube arrays, two photonic band gaps are emerged in the transmission spectra offing-shaped nanotube arrays, the two band gaps and transmission spectra are adjusted by the length, inner radius, intertube spacing and the dielectric constants of the core and embedding medium, and magnitude modification, redshift and blueshift of the resonance modes are observed. A metallic ring-shaped nanotube arrays for subwavelength band-stop filter in the range of visible light can be achieved. To understand its physical origin, field-interference mechanism was suggested by the field distributions. The proposed nanostructures and results may have great potential applications in subwavelength near-field optics.
文摘Large calculation error can be formed by directly employing the conventional Yee’s grid to curve surfaces.In order to alleviate such condition,unconditionally stable CrankNicolson Douglas-Gunn(CNDG)algorithm with is proposed for rotationally symmetric multi-scale problems in anisotropic magnetized plasma.Within the CNDG algorithm,an alternative scheme for the simulation of anisotropic plasma is proposed in body-of-revolution domains.Convolutional perfectly matched layer(CPML)formulation is proposed to efficiently solve the open region problems.Numerical example is carried out for the illustration of effectiveness including the efficiency,resources,and absorption.Through the results,it can be concluded that the proposed scheme shows considerable performance during the simulation.
基金Project(41174061) supported by the National Natural Science Foundation of ChinaProject(2011QNZT011) supported by the Free Exploration Program of Central South University,China
文摘The absorbing boundary is the key in numerical simulation of borehole radar.Perfect match layer(PML) was chosen as the absorbing boundary in numerical simulation of GPR.But CPML(convolutional perfect match layer) approach that we have chosen has the advantage of being media independent.Beginning with the Maxwell equations in a two-dimensional structure,numerical formulas of finite-difference time-domain(FDTD) method with CPML boundary condition for transverse electric(TE) or transverse magnetic(TM) wave are presented in details.Also,there are three models for borehole-GPR simulation.By analyzing the simulation results,the features of targets in GPR are obtained,which can provide a better interpretation of real radar data.The results show that CPML is well suited for the simulation of borehole-GPR.
基金supported by the National Natural Science Foundation of China(61571022611971022)。
文摘To efficiently simulate and calculate the radar cross section(RCS) related electromagnetic problems by employing the finite-difference time-domain(FDTD) algorithm, an efficient stretched coordinate perfectly matched layer(ESC-PML) based upon the exponential time differencing(ETD) method is proposed.The proposed implementation can not only reduce the number of auxiliary variables in the SC-PML regions but also maintain the ability of the original SC-PML in terms of the absorbing performance. Compared with the other existed algorithms, the ETDFDTD method shows the least memory consumption resulting in the computational efficiency. The effectiveness and efficiency of the proposed ESC-PML scheme is verified through the RCS relevant problems including the perfect E conductor(PEC) sphere model and the patch antenna model. The results indicate that the proposed scheme has the advantages of the ETD-FDTD method and ESC-PML scheme in terms of high computational efficiency and considerable computational accuracy.
基金supported by the National Key Laboratory of Science and Technology on Space Microwave(6142411032201)the National Key Research and Development Program of China(2020YFB1807400)+2 种基金the National Natural Science Foundation of China(6157102261971022)the National Key Laboratory Foundation of China(61424020305)。
文摘In order to simulate metamaterial rotational symmetric open region problems,unconditionally stable perfectly match layer(PML)implementation is proposed in the body of revolution(BOR)finite-difference time-domain(FDTD)lattice.More precisely,the proposed algorithm is implemented by the Crank-Nicolson(CN)Douglas-Gunn(DG)procedure for BOR metamaterial simulation.The constitutive relationship of metamaterial can be expressed by the Drude model and calculated by the piecewise linear recursive convolution(PLRC)approach.The effectiveness including absorption,efficiency,and accuracy is demonstrated through the numerical example.It can be concluded that the proposed implementation is to take the advantages of the CNDG-PML procedure,PLRC approach,and BORFDTD algorithm in terms of considerable accuracy,enhanced absorption and remarkable efficiency.Meanwhile,it can be demonstrated that the proposed scheme can maintain its unconditional stability when the time step exceeds the CourantFriedrichs-Levy(CFL)condition.
基金This work was supported by the National Natural Science Foundation of China(6157102261971022).
文摘An unsplit-field higher order nearly perfectly matched layer(NPML)based on the auxiliary differential equation approach is introduced in three-dimensional finite-difference timedomain lattices.The proposed scheme has the advantage of both the NPML scheme and the higher order concept in terms of the improved absorbing performance and considerable computational efficiency.By incorporating with the generalized material independent concept,the proposed implementation is indepen dent of the material’s type.Thus,it has the advantages of terminating arbitrary media without changing the updated equations in the PML regions.Its effectiveness and efficiency is further demonstrated through numerical examples.
基金supported by the Key Laboratory of Millimeter Waves of China (K200907)
文摘Because the conventional ultra wideband（UWB） radar imaging algorithm cannot meet the demand in the capability of multiple targets detection,a novel UWB radar imaging algorithm based on the near field radiation theory of dipole is presented.On the foundation of researching the principle of a time domain imaging algorithm,the back projection（BP） algorithm is derived and analyzed.Firstly,the far field sampling data are transferred to the near field sampling data by using the near field radiation theory of dipole.Then the BP algorithm is applied to target detection.The capability of the new algorithm to detect the multi-target is verified by using the finite-difference time-domain method,and the threedimensional images of targets are obtained.The coupling effect between targets for imaging is analyzed.The simulation results show that the new UWB radar imaging algorithm based on the near field radiation theory of dipole could weaken the coupling effect for imaging,and as a result the quality of imaging is improved.
基金supported by the National Natural Science Foundation of China(61401361)the Fundamental Research Funds for the Central Universities of China(31020150104)
文摘To handle the electromagnetic problems of the bi-static radar cross section （RCS） calculation of scatterer in a wide fre- quency band, a finite-difference time-domain （FDTD） extrapolation method combining with discrete Fourier transform （DFT） is pro- posed. By comparing the formulas between the steady state field extrapolation method and the transient field extrapolation method, a novel extrapolation method combining with DFT used in FDTD is proposed when a transient field incident wave is introduced. With the proposed method, the full-angle RCS distribution in a wide fre- quency band can be achieved through one-time FDTD calculation. Afterwards, the back-scattering RCS distributions of a double olive body and a sphere-cone body are calculated. Numerical results verify the validity of the proposed method.
