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1.
Cheng-Fu Yang 《中国物理 B》2022,31(8):84101-084101
Reusable reciprocal invisibility and phantom device is proposed and designed based on multi-folded transformation optics and equivalent components. In comparison with the reported reciprocal invisibility cloaks, the material parameters of the device presented here are homogeneous, and the hiding of the target object does not require any "anti-object" at all, which dramatically breaks through the limitations of the "anti-object" design in previous reciprocal cloak design. Perfectly illusion effect is also found by reasonably setting the material parameters of the restored medium of the device, which can be used to confuse detection radars while hiding target objects. Last but not least, the proposed device has an open structure, which enables the target object enclosed by the device to perform material exchange and simplex transfer of information with the outside world through open channels. In other words, the proposed device has a reusable function, enabling stealth or phantom of new target objects without changing any parameters of the device. 相似文献
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Manipulating surface plasmon waves by transformation optics:Design examples of a beam squeezer,bend,and omnidirectional absorber
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We present several design examples of how to apply transformation optics and curved space under coordinate transformation to manipulating the surface plasmon waves in a controlled manner.We demonstrate in detail the design procedure of the plasmonic wave squeezer,in-plane bend and omnidirectional absorber.We show that the approximation method of modifying only the dielectric material of a dielectric-metal surface of the plasmonic device could lead to acceptable performance,which facilitates the fabrication of the device.The functionality of the proposed plasmonic device is verified using three-dimensional full-wave electromagnetic simulations.Aiming at practical realization,we also show the design of a plasmonic in-plane bend and omnidirectional absorber by an alternative transformation scheme,which results in a simple device structure with a tapered isotropic dielectric cladding layer on the top of the metal surface that can be fabricated with existing nanotechnology. 相似文献
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Object coated with plasma has stimulated great interests of many people because of its stealth capability. The study on a conducting cylinder coated with coaxial plasma is very much, but there are little works on a conducting cylinder coated with eccentric plasma. In this article, a model for a conducting cylinder coated with eccentric unmagnetized plasma is set up, the scattering cross section of the object cylinder is studied by adopting the superposition of cylindrical wave functions and the coordinate transformation, where these wave functions are the solutions of Maxwell's equations with boundary conditions in cylindrical coordinates. The results show that the radar cross section for a conducting cylinder coated with eccentric plasma in every direction decrease obviously with an increase of the distance between two eccentric axes, but is almost not impacted by electron–neutral collision frequency of plasma, and the backscattering cross section of the target reduce with the increase of electron density. Comparing with the coaxial model, the backscattering cross section of the eccentric model has a smaller value in a wide frequency band. This is of significance for the target plasma stealth technology in practice. 相似文献
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Design of square-shaped heat flux cloaks and concentrators using method of coordinate transformation
A square-shaped heat flux cloak and a square-shaped heat flux concentrator have been designed theoretically according to the invariance symmetry of steady state thermal conductive equation. The direction of heat flux in these devices can be modulated as desired. Using the method of coordinate transformation, the inhomogeneous and anisotropic thermal conductivity in the transformation region have been acquired. Two-dimensional finite element simulations were performed to confirm the theoretical results. 相似文献
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Manipulating surface plasmon waves by transformation optics: Design examples of beam squeezer, bend, and omnidirectional absorber
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We present several design examples of how to apply the transformation optics and curved space under coordinate transformation to manipulating the surface plasmon waves in a controlled manner. We demonstrate in detail the design procedure of the plasmonic wave squeezer, in-plane bend and omnidirectional absorber. We show that the approximation method of modifying only the dielectric material of a dielectric-metal surface of the plasmonic device could lead to acceptable performance, which facilitates the fabrication of the device. The functionality of the proposed plasmonic device is verified using three-dimensional full-wave electromagnetic simulations. Aiming at practical realization, we also show the design of plasmonic in-plane bend and omnidirectional absorber by an alternative transformation scheme, which results in simple device structure with a tapered isotropic dielectric cladding layer on the top of the metal surface that can be fabricated with the existing nanotechnology. 相似文献
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We consider a non-Hermitian medium with a gain and loss symmetric, exponentially damped potential distribution to demonstrate different scattering features analytically. The condition for critical coupling (CC) for unidirectional wave and coherent perfect absorption (CPA) for bidirectional waves are obtained analytically for this system. The energy points at which total absorption occurs are shown to be the spectral singular points for the time reversed system. The possible energies at which CC occurs for left and right incidence are different. We further obtain periodic intervals with increasing periodicity of energy for CC and CPA to occur in this system. 相似文献
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结合改进的物理光学法和图形计算电磁学法实现了考虑边缘绕射情况下复杂目标的高频电磁波散射的高效且精确求解.传统的考虑边缘绕射的物理光学算法不能直接计算出目标的雷达截面,它需要先计算绕射贡献,然后加上物理光学的散射贡献,最终才能得到目标的雷达截面.通过运用改进的物理光学法对图形计算电磁学法进行修正,直接修正表面法向量,从而修正了表面电流,这样就考虑了边缘处的绕射,提高了算法的效率.这不但充分利用了计算机硬件优势,借助于计算机显示技术,由图形加速卡完成最困难、最费时的消隐工作,而且利用图形计算电磁学的积分公式,将三维空间的积分转化为屏幕像素的二维空间积分,使得计算大幅简化.数值结果表明了所提出方法的精确性和高效性. 相似文献
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Lateral shift dependence of spontaneous emission in a planar
cavity with perfect conducting cladding
R. Tan G.-X. Li Y.-P. Yang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(2):341-346
We consider the effect of lateral shift of the “beams" resulting
from the atom emissions on spontaneous decay of an excited atom
embedded in a planar cavity with perfect conducting cladding. It is
found that the spontaneous decay could be enhanced or suppressed
owing to the positive and negative lateral shift at the interfaces
of the cavity mirror. Compared with the emission between two perfect
conducting plates, the surface guided modes could exist and for very
thin planar cavity, the density of surface guided modes may be
obviously larger than those of the propagating guided modes. 相似文献
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Shakeel Ahmed 《Optics Communications》2008,281(23):5664-5670
Electromagnetic scattering of an incident uniform plane wave from a perfect electromagnetic conductor (PEMC) circular cylinder, coated with a metamaterial is investigated theoretically. In the analysis the coating layer may be double-positive (DPS), double-negative (DNG), epsilon-negative (ENG) or mu-negative (MNG). It is assumed that both PEMC cylinder and the coating layer are infinite along the cylinder axis. Both parallel and perpendicular polarization cases are considered for the analysis. Comparison between the monostatic and bistatic echo widths, of a PEMC cylinder coated with metamaterial and coated with ordinary dielectric material (DPS), is presented. The numerical results are compared with the published literature, and comparison is found to be in good agreement. 相似文献
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A stranded wire rope is idealized as a homogeneous conducting and permeable cylinder of circular cross section and of infinite
length. The rope is excited by a coaxial solenoid or finite-length multi-turn coil that carries an azimuthally directed alternating
current. The rope and the enclosing solenoid may have a uniform velocity relative to each other. Using a nonrelativistic analysis,
the nature of this dynamic interaction is examined and numerical results are presented for parameter values that are relevant
to both static and dynamic conditions in nondestructive testing of such cylindrical conductors. It is shown that for motional
velocitiesv larger than about 50 m/s the dynamic interaction with the rope specimen is appreciably modified from that for the static
condition (i. e., forv=0). 相似文献
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The schlieren method is applied to visualizing the sound scattering ofa cylinder immersed in the liquids.Images of the echoes,caused by normal andoblique incidence from a cylinder,are obtained for two kinds of liquids:(1)theliquid is composed of a transparent liquid;and(2)the liquid is composed of twonon-mixable transparent liquids.It is found experimentally that the echo canbe caused by the discontinaites in the shadow zone.This fact is utilized to dem-onstrate the locus of the helical surface wave creeping along the surface of thecylinder.For such cases the three-dimensional image can be described by thismethod and has not to use the system with special appliances and complexalgorithm. 相似文献
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Michael Sztucki Jacques Gorini Jean‐Pierre Vassalli Loys Goirand Pierre Van Vaerenbergh Theyencheri Narayanan 《Journal of synchrotron radiation》2008,15(4):341-349
An improved crystal design for a Bonse–Hart ultra‐small‐angle scattering instrument is presented. Defects at the diffracting surfaces of the conditioning crystals were found to be at the origin of diffuse scattering that enhances the intensity in the wings of the rocking curves by several orders of magnitude. In order to improve the performance of the instrument, the monolithic channel‐cut crystals were replaced by pairs of separate polished and deeply etched crystals. These crystals were mounted on a mechanical stage that allows very precise parallel alignment of the crystals to within a tiny fraction of the rocking curve width (sub‐µrad range). By using these double‐crystal set‐ups, the parasitic background scattering was reduced by more than an order of magnitude. The steps to achieve the optimum surface quality of the crystals as well as the precision mechanical design for their parallel alignment are described. Significant improvement of the signal‐to‐background ratio and the available wavevector range of the instrument make it suitable for studying the microstructure and dynamics of dilute and weakly scattering soft‐matter systems. This development also has potential applications in X‐ray optics such as low‐background and tunable monochromators and collimators. 相似文献
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The results of this paper were presented at the All-Union Scientific-Technical Conference on Radio Receiving Devices in the city of Gorki in 1985. 相似文献
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《Waves in Random and Complex Media》2013,23(3):389-404
A hybrid integral equation is developed to solve the problem of electromagnetic (EM) scattering from a three-dimensional (3D) perfect electric conducting (PEC) object above a two-dimensional (2D) PEC or dielectric Gaussian rough surface. Firstly, the Kirchhoff–Helmholtz (KH) equation is adopted to describe the wave reflection on the rough surface; only one integral operation on the rough surface is needed, and the scattering from the object can be described by solving the electric field integral equation (EFIE) on the surface of the object. Moreover, according to scattering theory, the KH equation and the EFIE are coupled together (KH-EFIE) to describe wave propagation between the object and the rough surface. Then method of moments (MoM) is adopted to solve the KH-EFIE, and the current is obtained to calculate the scattering field. Finally, compared with other methods, the accuracy of the proposed approach is validated, and its efficiency is proved to be much higher than numerical solutions. Furthermore, by calculating the statistic composite radar cross-section (RCS) of the object/surface and the difference radar cross-section (DRCS) of the object, the influence of the rough surface root mean square (rms) height, the correlation length, the medium permittivity, the shape of the object, and the altitude of the object on the scattering characteristic is investigated. 相似文献
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Electromagnetic scattering from an infinite and a finite length PEMC circular cylinder, illuminated by an arbitrarily oriented
dipole, is investigated theoretically. An electric dipole as a source of excitation is considered first, and then a magnetic
dipole as a source of excitation is treated. In contrast to the case of an axially directed dipole, it is shown that no additional
terms are needed to incorporate the cross-polarized component of the field for the case of radial and circumferential dipoles.
Numerical verifications are presented to verify the validity of derived results and numerical code by comparing results with
the published literature.
相似文献