scholarly journals Designing the collective non-local responses of metasurfaces

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
James R. Capers ◽  
Stephen J. Boyes ◽  
Alastair P. Hibbins ◽  
Simon A. R. Horsley
Keyword(s):  
Degrees Of Freedom ◽  
Near Field ◽  
Electromagnetic Properties ◽  
Local Responses ◽  
Electric Polarizabilities ◽  
Scattering Effects ◽  
Field Radiation ◽  
Non Local ◽  
Properties Of Materials ◽  
Multiple Scattering Effects

AbstractThe ability to design the electromagnetic properties of materials to achieve any given wave scattering effect is key to many technologies, from communications to cloaking and biological imaging. Currently, common design methods either neglect degrees of freedom or are difficult to interpret. Here, we derive a simple and efficient method for designing wave–shaping materials composed of dipole scatterers, taking into account multiple scattering effects and both magnetic and electric polarizabilities. As an application of our theory, we design aperiodic metasurfaces that re-structure the radiation from a dipole emitter: (i) modifying of the near-field to provide a 4-fold enhancement in power emission; (ii) re-shaping the far-field radiation pattern to exhibit chosen directivity; and (iii) the design of a discrete Luneburg–like lens. Additionally, we develop a clear physical interpretation of the optimised structure, by extracting eigen-polarizabilities of the system, finding that a large eigen-polarizability corresponds to a large collective response of the scatterers.

MULTIPLE SCATTERING EFFECTS IN THE COBALT K-EDGE EXAFS OF METAL CARBONYL COMPLEXES

1986 ◽  
Vol 47 (C8) ◽  
pp. C8-589-C8-592
Author(s):  
N. BINSTED ◽  
S. L. COOK ◽  
J. EVANS ◽  
R. J. PRICE ◽  
G. N. GREAVES
Keyword(s):  
Multiple Scattering ◽  
Metal Carbonyl ◽  
Carbonyl Complexes ◽  
Metal Carbonyl Complexes ◽  
Scattering Effects ◽  
Multiple Scattering Effects

Local and non-local damage model with extended stress decomposition for concrete

2021 ◽  
pp. 105678952199872
Author(s):  
Bilal Ahmed ◽  
George Z Voyiadjis ◽  
Taehyo Park
Keyword(s):  
Shear Stress ◽  
Degrees Of Freedom ◽  
Biaxial Loading ◽  
Damage Model ◽  
Local Model ◽  
Uniaxial Tensile ◽  
Gradient Theory ◽  
Principal Stresses ◽  
Stress Decomposition ◽  
Non Local

In this work, a new damage model for concrete is proposed with an extension of the stress decomposition (limited to biaxial cases), to capture shear damage due to the opposite signed principal stresses. To extract the pure shear stress, the assumption is made that one component of the shear stress is a minimum absolute of the two principal stresses. The opposite signed principal stresses are decomposed into shear stress and uniaxial tensile/compressive stress. A local model is implemented in Abaqus UMAT and it is further extended to a non-local model by utilization of the gradient theory. The concept of three length scales (tension, compression, and shear) is kept the same as the recently proposed nonlocal damage model by the authors. The nonlocal model is implemented in the Abaqus UEL-UMAT subroutine with an eight-node quadrilateral user-defined element, having five degrees of freedom at corner nodes (displacement in X/Y direction and tensile/compressive and shear nonlocal equivalent strain) and two degrees of freedom at internal nodes. Some examples of a local model including uniaxial and biaxial loading are addressed. Also, five examples of mixed crack mode and mode-I cracking are presented to comprehensively show the performance of this model.

Applications of metamaterial sensors: a review

2021 ◽  
pp. 1-15
Author(s):  
Divya Prakash ◽  
Nisha Gupta
Keyword(s):  
Electromagnetic Interaction ◽  
High Sensitivity ◽  
Ring Resonators ◽  
Electromagnetic Properties ◽  
Physical Parameters ◽  
Split Ring ◽  
Split Ring Resonators ◽  
Quality Testing ◽  
Properties Of Materials ◽  
Metamaterial Absorbers

Abstract Sensors based on metamaterial absorbers are very promising when it comes to high sensitivity and quality factor, cost, and ease of fabrication. The absorbers could be used to sense physical parameters such as temperature, pressure, density as well as they could be used for determining electromagnetic properties of materials and their characterization. In this work, an attempt has been made to explore the various possible applications of these sensors. Metamaterial-based sensors are very popular for its diverse applications in areas such as biomedical, chemical industry, food quality testing, agriculture. Split-ring resonators with various shapes and topologies are the most frequently used structures where the sensing principle is based on electromagnetic interaction of the material under test with the resonator. Overcoming the design challenges using metamaterial sensors involving several constraints such as cost, compactness, reusability, ease in fabrication, and robustness is also addressed.

Reconstruct the PWM Signal of Switching Power Supplies from the Near Field Radiation

2013 ◽  
Vol 718-720 ◽  
pp. 1792-1796
Author(s):  
Zhong Qun Li ◽  
Kai Xie ◽  
Ying Hao Ye ◽  
Rong Bin Guo ◽  
Xu Fei Wang
Keyword(s):  
Pulse Width Modulation ◽  
Signal Reconstruction ◽  
Near Field ◽  
Buck Converter ◽  
Power Supplies ◽  
Switching Converters ◽  
Switching Power ◽  
Magnetic Components ◽  
Field Radiation ◽  
Switching Power Supplies

A non-contact testing method is proposed for encapsulation treated or insulation coated switching power supplies, which is implemented by reconstructing the pulse width modulation (PWM) signal of switching converters from the near field radiation of magnetic components. The radiation pattern of a buck converter is investigated, and the magnetic field sensing probe and PWM signal reconstruction circuit are also illustrated. The reconstruction testing is carried out on a buck converter; the duty cycle error of the reconstructed PWM signal is less than 0.2%, which validates the proposed method.

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