Protective effect of silicone-modified epoxy resin coating on iron-based materials against sulfate-reducing bacteria-induced corrosion

Abstract Using conformal transformation optics, a cylindrical shell made of an isotropic refractive index material is designed to improve the directivity of a wire antenna while making it unidirectionally invisible. If the incident wave comes from a specific direction, it is guided around the wire. Furthermore, when an electrical current is used to excite the wire, the dielectric shell transforms the radiated wave into two lateral beams, improving directivity. The refractive index of the dielectric shell is calculated using the transformation optics recipe after establishing a closed-form conformal mapping between an annulus and a circle with a slit. The refractive index is then modified and discretized using a hexagonal lattice. Ray-tracing and full-wave simulations with COMSOL Multiphysics are used to validate the functionality of the proposed shell. 

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Strictly conformal transformation optics for directivity enhancement and unidirectional cloaking of a cylindrical wire antenna

• Using higher transformations inside the ONM to make design. • Regardless of the shape of the concealed region, the material parameters of the designed cloak remain unchanged. • Can be realized by only natural materials, i.e., metallic channels filled with dielectrics, whose refractive indices take a range determined only by the size of the cloak. • Nearly perfect invisibility effect for any type of detecting wave incident from any angle. A full space omnidirectional cloak with an optic-null medium (ONM) shell and an isotropic homogeneous restoring core is designed by thrice coordinate transformations inside ONM. The designed cloak can be realized by subwavelength dielectric channels enclosed with metallic plates and a uniform dielectric restoring core in air, i.e., no metamaterials or waveguide structures are required. Different from previous studies, the electromagnetic parameters of the designed cloak in this study are strict in accordance with transformation optics (no simplifications), which can achieve a nearly perfect omnidirectional cloaking effect at the design frequency by natural materials. Due to the transformation-invariant feature of the ONM, the shape, size and position of the concealed region can be adjusted freely, while the material parameters of the corresponding cloak remain unchanged. 

A metamaterial-free omnidirectional invisibility cloak based on thrice transformations inside optic-null medium

Cloaks can greatly reduce the scattering cross-section of hidden objects through various mechanisms, thereby making them invisible to outside observers. Among them, the full-space omnidirectional cloak based on transformation optic with full parameters are difficult to realize without metamaterials and often needs to be simplified before realization, while most cloaks with simplified parameters have limited working direction and cannot achieve omnidirectional cloaking effect. In this study, a full-space omnidirectional cloak is designed based on transformation optics and optic-null medium, which only needed natural materials without metamaterials. The designed omnidirectional cloak is realized by subwavelength metal channels filled with isotropic dielectrics whose refractive indices range from 1 to 2, which is homogeneous in each channel. The numerical simulation results verify good scattering suppression effect of the designed cloak for various detecting waves.

Full-space omnidirectional cloak by subwavelength metal channels filled with homogeneous dielectrics.

New strategy for impedance measurement of surface oxidation characteristic in ceramic fiber by controlling aspect ratio

The method to elaborately design the refractive index profile in the lower Riemann sheet of Zhukovski transformation plays an important role in the performance of this kind of conformal cloaks. However, for most proposed schemes, the mathematical calculations are complex. Here, we propose a more convenient method to design conformal cloaks by manipulating structures directly in the physical space. The designed cloak only needs symmetrical metal boundaries filled with normal dielectrics (refractive index ranges from 1 to 2) in the 'circular branch cut', which would be more feasible for future experimental implementation. Numerical simulations are performed by using the finite element method to validate our theoretical analysis.

Designing conformal cloaks by manipulating structures directly in the physical space.

Nonlinear conductivity characteristics of epoxy resin-impregnated nano-SiC-modified insulating paper

We report a widely tunable monolithically integrated V-coupled cavity interband cascade laser (ICL) emitting near $3.4~\mu \text{m}$ . The mode selection is achieved using a half-wave V-coupler designed for the ICL in the mid-infrared range without any grating. The side-mode suppression ratio is demonstrated up to 35.7 dB. In the heat-sink temperature range from 130 K to 140 K, single-mode wavelength tuning range of over 100 nm from 3329.9 nm to 3431.3 nm has been attained by adjusting both current and temperature. These results show that the V-coupled cavity ICLs are very promising for multi-species trace gas absorption spectroscopy with a high sensitivity.

Zhanyi Wang

Papers

Designing conformal cloaks by manipulating structures directly in the physical space.

Nonlinear conductivity characteristics of epoxy resin-impregnated nano-SiC-modified insulating paper

Single-Mode Tunable Interband Cascade Laser Emitting at 3.4 μm With a Wide Tuning Range Over 100 nm