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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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We demonstrate the possibility of creating a time gap in the slow light based on spectral hole burning in a fourlevel Doppler broadened sodium atomic system. A time gap is also observed between the slow and the fast light in the hole burning region and near the burnt hole region, respectively. A cloaking time gap is attained in microseconds and no distortion is observed in the transmitted pulse. The width of the time gap is observed to vary with the inverse Doppler effect in this system. Our results may provide a way to create multiple time gaps for a temporal cloak. 相似文献
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Transformation optics provides great versatility for precisely manipulating electromagnetic waves. It has been extended to other fields including acoustics, thermotics, and electrics. Taking advantage of the transformation electrics method, we demonstrate that the square-shaped cloak can guide electric current around the cloaked region smoothly without perturbing the exterior electric current. And the cylindrical rotator can rotate the electric current.Inside the enclosed domain of the rotator, the electric current from the outside will appear as if it is coming from a different angle. Finally, the related experimental realizations and potential applications are also discussed. 相似文献
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《Laser \u0026amp; Photonics Reviews》2017,11(6)
A method is introduced for the design of invisibility cloaks inspired by fluid dynamics that is different from traditional transformation optics. The inhomogeneous refractive index of the liquid cloak controlled by the natural liquid diffusion is analogous to its counterpart designed by transformation optics. Here, a tunable liquid visible cloak is experimentally presented by the natural diffusion of miscible flows. This method avoids the use of complex nanostructures in its solid counterpart, and provides a simple and low‐cost approach. This implies that optofluidics can be used as a technology to make real‐time reconfigurable transformation optic devices. 相似文献
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An illusion counter-part displays the same scattering far-field pattern as that of a real object. In this paper, for the first time, we demonstrate that such an unreal illusion can be cloaked by an external cloak. This phenomenon shall be called ??cloak an illusion??. Numerical simulations were performed to demonstrate such a phenomenon. 相似文献
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A novel cloaking scheme to hide an object in a half space from electromagnetic (EM) detection without reflection is firstly presented. The proposed cloaking scheme contains a couple of matching strips, which consist of an isotropic material layer and an anisotropic UPML layer, located right under the bottom surface of a semi-cylindrical cloaking shell. Simple expressions for the material parameters of the cloaking scheme are derived. Numerical simulations are also performed, and a good cloaking effect is achieved. The cloaking scheme is effective to hide the local object with strong scattering characters placed on mobile carriers, such as the radar antenna system on an aircraft.1 相似文献
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基于多层复合材料结构的二维声隐身斗篷设计思想, 利用主动隔膜声学空腔有效密度可以任意控制这一特性, 设计了主动声学超材料下的无限长圆柱声隐身斗篷. 给出了主动隔膜声学空腔单元的声电元件类比模拟电路图和具体的有效密度控制方法. 进行了主动声学超材料声隐身斗篷的结构建模, 并对平面入射波入射下此圆柱隐身斗篷周围声压分布场进行仿真计算. 结果表明, 平面波在一定频率范围内可以毫无阻碍地透过圆柱斗篷, 似乎不存在这种障碍物, 达到声隐身效果. 同时, 计算了主动声材料斗篷下总散射截面随频率变化曲线, 研究了此斗篷隐身效果随频率的变化特性. 本文从主动控制角度探讨实验实现隐身斗篷的技术问题, 有望给声隐身斗篷实验设计提供一条新的技术途径. 相似文献
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基于等效介质理论, 提出了具有共焦层状结构的椭圆柱形声隐身衣设计方法. 理论分析与有限元数值模拟表明, 所设计隐身衣依然具有完美隐身衣典型特征, 可使刚性圆柱体散射场明显减小, 并且在隐身衣区域表现出波阵面弯曲的特性, 同时在隐身衣外部波阵面保持不变. 增加隐身衣离散层数可以拓宽其有效工作频带, 改善隐身效果. 由于是一种线变换隐身衣, 隐身效果受到了入射波方向的影响, 只有当入射波方向与椭圆长轴平行时效果最佳. 另外当椭圆柱焦距非常小的时候, 可近似认为是圆柱形隐身衣. 仿真实验结果证明了方法的正确性. 该研究为实现复杂形状声隐身衣提供了一种有效途径. 相似文献