Multifrequency cloak with multishell by using transformation medium

2009 ◽  
Vol 105 (12) ◽  
pp. 124505 ◽  
Author(s):  
Y. Gao ◽  
J. P. Huang ◽  
K. W. Yu
Keyword(s):  
Transformation Medium

Design of a Wave Shifter with the Exit Direction Controllable Based on Coordinate Transformation Theory

2013 ◽  
Vol 798-799 ◽  
pp. 590-593
Author(s):  
Wen Yan Yan ◽  
You Gang Ke
Keyword(s):  
Numerical Simulations ◽  
Coordinate Transformation ◽  
Longitudinal Axis ◽  
The Other ◽  
Wave Direction ◽  
Transformation Theory ◽  
Transformation Medium ◽  
Theoretical Design ◽  
Constitutive Parameters

We propose a wave shifter with the exit wave direction controllable by using a transformation-medium slab. The coordinate transformation takes two steps. One is along the longitudinal axis to realize shift and the other is on the transversal axis to adjust the exit directon. By using coordinate transformation theory, the constitutive parameters of the slab are obtained. Numerical simulations are further given to validate the performance of the theoretical design.

Novel Microstrip Antenna Design Upon Transformation Medium

2015 ◽  
Vol 14 ◽  
pp. 543-546 ◽  
Author(s):  
Zhan Zhang ◽  
Shouliang Li ◽  
Junhong Wang
Keyword(s):  
Microstrip Antenna ◽  
Antenna Design ◽  
Transformation Medium

scholarly journals Broadband corner cloak using a uniaxial transformation medium of stacked artificial dielectric sheets

2020 ◽  
Vol 7 ◽  
pp. 4
Author(s):  
Yuma Takano ◽  
Atsushi Sanada
Keyword(s):  
Cross Sections ◽  
Near Field ◽  
Field Measurements ◽  
Corner Reflector ◽  
Specular Scattering ◽  
Transformation Medium ◽  
Field Distributions ◽  
Artificial Dielectric ◽  
Measured Field ◽  
Original Area

We demonstrate corner cloak operations mimicking a corner reflector and hiding objects in a truncated corner. The corner cloak is designed at 18.25 GHz and implemented by nonresonant artificial dielectric sheets stacked onto the bottom hypotenuse. It is shown by the near-field measurements that the measured field distributions for the cloak agree well with those for the original area of the corner reflector as well as those for the numerical prediction. The bistatic radar cross-sections (BRCSs) for the cloak and the original area calculated from the measured field distributions coincide with each other and the cloak operation is quantitatively confirmed. The bandwidth evaluated by the specular scattering angles from the BRCSs shows broadband operation as wide as from 16 to 22 GHz.

Controlling Out-of-Plane Shear Wave Propagation With Broadband Cloaking

2019 ◽  
Author(s):  
Mao Liu ◽  
W. D. Zhu
Keyword(s):  
Linear Transformation ◽  
Elastic Waves ◽  
Shear Waves ◽  
Nonlinear Transformation ◽  
Plane Shear ◽  
Shear Moduli ◽  
Transformation Medium ◽  
Invisibility Cloak ◽  
Independent Functions ◽  
Out Of Plane

Abstract A major challenge in designing a perfect invisibility cloak for elastic waves is that density and elasticity tensors need to be independent functions of its radius with a linear transformation medium. The traditional cloak for out-of-plane shear waves in membranes exhibits material properties with inhomogeneous and anisotropic shear moduli and densities, which yields a poor or even negative cloaking efficiency. This paper presents design of a cylindrical cloak for shear waves based on a nonlinear transformation. This excellent broadband nonlinear cloak only requires variation of its shear modulus, while the density in the cloak region remains unchanged. The nonlinear ray trajectory equation for out-of-plane shear waves is derived and a parameter to adjust the efficiency of the cylindrical cloak is introduced. Qualities of the nonlinear invisibility cloak are discussed by comparison with those of a cloak with the linear transformation. Numerical examples show that the nonlinear cloak is more effective for shielding out-of-plane shear waves from outside the cloak than the linear cloak and illustrate that the nonlinear cloak for shear waves remains highly efficient in a broad frequency range. The proposed nonlinear transformation in conjunction with ray trajectory equations can also be used to design nonlinear cloaks for other elastic waves.

scholarly journals Design of highly-efficient acoustic waveguide couplers using impedance-tunable transformation acoustics

2020 ◽  
Vol 34 (32) ◽  
pp. 2050250
Author(s):  
Jun Cao ◽  
Fenghua Qi ◽  
Senlin Yan ◽  
Lifa Zhang
Keyword(s):  
Refractive Index ◽  
Impedance Matching ◽  
Coupling Efficiency ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Low Frequencies ◽  
Acoustic Waveguide ◽  
Acoustic Coupling ◽  
Transformation Medium ◽  
Transformation Acoustics

In this paper, the theory of impedance-tunable transformation acoustics in the geometric-acoustics limit is proposed to design efficient two-dimensional acoustic waveguide couplers. By choosing suitable impedance functions in the original space, impedance matching between the transformation medium and the background medium becomes possible, and the reflection at the boundary is reduced. The theory can be used to enable efficient acoustic coupling between waveguides of different sizes and different embedded media. By selecting an appropriate impedance function and a tunable acoustic refractive index, the transformed medium in the coupler can become a simplified parameter medium, for which the bulk modulus is a constant. This makes the experiment substantially easier. The problem of a reduced coupling-efficiency at low frequencies (a deviation from the geometric acoustic approximation) can be mitigated by selecting a large acoustic refractive index. Our two-dimensional numerical simulations indicate that this theoretical design works very well. The method can be extended to other transformation acoustic designs including three-dimensional cases.

Wave Shape Transformers Based on Transformation Medium Slabs

2013 ◽  
Vol 712-715 ◽  
pp. 1811-1815
Author(s):  
You Gang Ke ◽  
Fu Gui Yang ◽  
Liang Qiao
Keyword(s):  
Numerical Simulations ◽  
Gaussian Beam ◽  
Coordinate Transformations ◽  
Wave Shape ◽  
Transformation Medium ◽  
Theoretical Design ◽  
Planar Wave ◽  
Constitutive Parameters ◽  
Wave Shapes ◽  
Beam Collimation

We propose wave shape transformers using slab transformation media which can transform planar wave shapes to convex or concave ones. By finite embedded coordinate transformations, a transformation is established from a parabola to a plane and the constitutive parameters of slabs are obtained. Numerical simulations are given to validate the performance of the theoretical design. Using such transformers, Gaussian beam collimation and focusing can be realized.

scholarly journals Directivity enhancement of a cylindrical wire antenna by a graded index dielectric shell designed using strictly conformal transformation optics

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hossein Eskandari ◽  
Soorena Saviz ◽  
Tomáš Tyc
Keyword(s):  
State Of The Art ◽  
Effective Medium Theory ◽  
Wire Antenna ◽  
Comsol Multiphysics ◽  
Medium Theory ◽  
Graded Index ◽  
Transformation Medium ◽  
Full Wave ◽  
Dielectric Shell ◽  
Cylindrical Wire

AbstractA transformation-optical method is presented to enhance the directivity of a cylindrical wire antenna by using an all-dielectric graded index medium. The strictly conformal mapping between two doubly connected virtual and physical domains is established numerically. Multiple directive beams are produced, providing directive emission. The state-of-the-art optical path rescaling method is employed to mitigate the superluminal regions. The resulting transformation medium is all-dielectric and nondispersive, which can provide broadband functionality and facilitate the realization of the device using available fabrication technologies. The realization of the device is demonstrated by dielectric perforation based on the effective medium theory. The device’s functionality is verified by carrying out both ray-tracing and full-wave simulations using finite-element-based software COMSOL Multiphysics.

scholarly journals The Adhesion-Associated sca Operon inStreptococcus gordonii Encodes an Inducible High-Affinity ABC Transporter for Mn2+ Uptake

1998 ◽  
Vol 180 (2) ◽  
pp. 290-295 ◽  
Author(s):  
Paul E. Kolenbrander ◽  
Roxanna N. Andersen ◽  
Rachel A. Baker ◽  
Howard F. Jenkinson
Keyword(s):  
Abc Transporter ◽  
Binding Protein ◽  
Transformation Process ◽  
Atp Binding ◽  
Wild Type ◽  
High Affinity ◽  
Transformation Medium ◽  
Low Concentrations ◽  
Atp Binding Protein ◽  
Mutant Cells

ABSTRACT ScaA lipoprotein in Streptococcus gordonii is a member of the LraI family of homologous polypeptides found among streptococci, pneumococci, and enterococci. It is the product of the third gene within the scaCBA operon encoding the components of an ATP-binding cassette (ABC) transporter system. Inactivation ofscaC (ATP-binding protein) or scaA(substrate-binding protein) genes resulted in both impaired growth of cells and >70% inhibition of 54Mn2+ uptake in media containing <0.5 μM Mn2+. In wild-type andscaC mutant cells, production of ScaA was induced at low concentrations of extracellular Mn2+ (<0.5 μM) and by the addition of ≥20 μM Zn2+. Sca permease-mediated uptake of 54Mn2+ was inhibited by Zn2+ but not by Ca2+, Mg2+, Fe2+, or Cu2+. Reduced uptake of54Mn2+ by sca mutants and by wild-type cells in the presence of Zn2+ was abrogated by the uncoupler carbonylcyanide m-chlorophenylhydrazone, suggesting that Mn2+ uptake under these conditions was proton motive force dependent. The frequency of DNA-mediated transformation was reduced >20-fold in sca mutants. The addition of 0.1 mM Mn2+ to the transformation medium restored only partly the transformability of mutant cells, implying an alternate role for Sca proteins in the transformation process. Cells ofsca mutants were unaffected in other binding properties tested and were unaffected in sensitivity to oxidants. The results show that Sca permease is a high-affinity mechanism for the acquisition of Mn2+ and is essential for growth of streptococci under Mn2+-limiting conditions.

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