Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Two-Dimensional Structure-Embedded Acoustic Lenses based on Periodic
  Acoustic Black Holes   Recent studies have introduced a new class of two-dimensional acoustic
metamaterials whose dispersion and propagation properties results from the use
of geometric inhomogeneities in the form of Acoustic Black Holes (ABH). The ABH
is an element able to smoothly bend and slow down elastic waves, therefore
providing a variety of unconventional dispersion and propagation properties
typically observed in more complex multi-material and locally resonant designs.
This approach enables thin-walled structural elements having fully embedded
acoustic lenses capable of different functionalities such as focusing,
collimation, and negative refraction. Numerical simulations show that such
structures exhibit broadband operating conditions that span both the
metamaterial and the phononic range. Full field experimental measurements allow
validating the design approach and confirm the performance of the embedded
acoustic lens.

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The categories of this paper are: hep-ex
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The categories of this paper are: dg-ga
11
The categories of this paper are: hep-lat
19
The categories of this paper are: eess
18
The categories of this paper are: econ
37
The categories of this paper are: supr-con
4
The categories of this paper are: cond-mat
29
The categories of this paper are: funct-an
12
The categories of this paper are: nucl-th
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The categories of this paper are: gr-qc
22
The categories of this paper are: chao-dyn
6
The categories of this paper are: astro-ph
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The categories of this paper are: cs
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The categories of this paper are: stat
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The categories of this paper are: hep-th
32
The categories of this paper are: atom-ph