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Experimental verification of similarity criteria for sound absorption of simple metamaterials

Chojak Aleksandra

Vibrations in Physical Systems

2022

Vol. 33, nr 2

art. no. 2022211

The paper concerns the dimensional analysis of simple acoustic metamaterials and its experimental verification in a computer model. Due to their decreased thickness possible because of the thermoviscous losses and sound dispersion that occur in acoustic metamaterials, such structures are gaining popularity, both as sound absorbers and diffusers. This implies the need to find their equivalents to be used at scale - both for modeling interiors with metamaterials and developing more complicated structures. The paper discusses the dimensional analysis performed for a generalized unit cell of a metamaterial with a resonator. The dimensional analysis shows the need for scaling both the geometrical dimensions of the structure and the parameters of the medium - air. The dimensional analysis was derived based on the transfer matrix method and was proven correct with the finite element method model. The paper also discusses the consequences of neglecting the air criteria, which are impossible to be fulfilled. This opens the question of finding new criterial numbers allowing the correct reflection of acoustic metamaterials at scale.

Special optical communication filter based on Thue-Morse photonic crystal structure

Alipour-Banaei H., Serajmohammadi S., Mehdizadeh F., Hassangholizadeh-Kashtiban M.

Optica Applicata

2016

Vol. 46, nr 1

145--152

In this paper we proposed a novel narrowband optical filter for wavelength division multiplexing applications. Due to their high transmission efficiency and very narrowband properties, we used the 5th generation Thue-Morse structure for designing our proposed filter. But novelty of our work is introducing another ID photonic crystal structure as a defect structure into the Thue-Morse structure in order to create pass band inside the photonic band gap of the Thue-Morse structure. All of the simulations and calculations have been done using the transfer matrix method. The most interesting property of this filter is that by increasing the number of the periods of the ordinary 1D photonic crystal, the number of the pass bands increases.