scholarly journals Bending a periodically layered structure for transformation acoustics

2011 ◽  
Vol 98 (24) ◽  
pp. 241914 ◽  
Author(s):  
Zixian Liang ◽  
Jensen Li
Keyword(s):  
Layered Structure ◽  
Transformation Acoustics

An Acoustic Metamaterial Bending Waveguide Design Using Transformation Acoustics

2011 ◽  
Author(s):  
Liang-Yu Wu ◽  
Tzeh-Yi Chiang ◽  
Mei-Ling Wu ◽  
Lien-Wen Chen
Keyword(s):  
Layered Structure ◽  
Material Properties ◽  
Mass Density ◽  
Homogeneous Material ◽  
Two Dimensional ◽  
Negative Mass ◽  
Acoustic Metamaterial ◽  
Transformation Medium ◽  
Waveguide Design ◽  
Transformation Acoustics

An acoustic bending waveguide is designed by transformation acoustics. A two-dimensional square area with anisotropic and homogeneous material properties is transformed into a fan-shaped area with anisotropic and inhomogeneous material properties to rotate the direction of beam propagation. The transformation medium can be realized by alternating layered structure consisting of water and fluid with negative mass density. We propose that an acoustic metamaterial composed of three layers in water background can be designed to replace negative mass density fluid and achieve the acoustic bending waveguide.

Design and assessment of an acoustic ground cloak with layered structure

2015 ◽  
Vol 29 (27) ◽  
pp. 1550191 ◽  
Author(s):  
Jie Xiong ◽  
Tianning Chen ◽  
Xiaopeng Wang ◽  
Jian Zhu
Keyword(s):  
Layered Structure ◽  
Acoustic Waves ◽  
Effective Medium Theory ◽  
Incident Angle ◽  
Multilayered Structure ◽  
Assessment System ◽  
Cosine Similarity ◽  
Acoustic Beam ◽  
Medium Theory ◽  
Transformation Acoustics

In this paper, a two-dimensional acoustic ground cloak with alternating layered structure composed of mercury and water is designed on the basis of transformation acoustics and effective medium theory. The cloak exhibits excellent cloaking performance to hide an object from the detection of acoustic waves. Cosine similarity is proposed to precisely quantize and evaluate the cloaking performance, which turns out to be succinct and effective. Numerical simulations confirm that the cloak could work well in a broad frequency band in which the cloaking performance displays an oscillatory decrease with increasing frequency. In addition, the omnidirectional property, larger incident angle of the acoustic beam has the better cloaking performance, is analyzed. This multilayered structure of cloak may offer an access to fabrication simplicity and experimental demonstration. The concept of cosine similarity may be an enrichment of the assessment system for acoustic cloaks.

In situ TEM Studies of agglomeration of sub-nanometer Ru layers in Ru/C multilayers

1992 ◽  
Vol 50 (1) ◽  
pp. 256-257
Author(s):  
Tai D. Nguyen ◽  
Ronald Gronsky ◽  
Jeffrey B. Kortright
Keyword(s):  
Layered Structure ◽  
Driving Force ◽  
High Energy ◽  
Superior Performance ◽  
In Situ Tem ◽  
Rayleigh Instability ◽  
Practical Applications ◽  
Transmission Electron ◽  
Diffraction Patterns

Nanometer period Ru/C multilayers are one of the prime candidates for normal incident reflecting mirrors at wavelengths < 10 nm. Superior performance, which requires uniform layers and smooth interfaces, and high stability of the layered structure under thermal loadings are some of the demands in practical applications. Previous studies however show that the Ru layers in the 2 nm period Ru/C multilayer agglomerate upon moderate annealing, and the layered structure is no longer retained. This agglomeration and crystallization of the Ru layers upon annealing to form almost spherical crystallites is a result of the reduction of surface or interfacial energy from die amorphous high energy non-equilibrium state of the as-prepared sample dirough diffusive arrangements of the atoms. Proposed models for mechanism of thin film agglomeration include one analogous to Rayleigh instability, and grain boundary grooving in polycrystalline films. These models however are not necessarily appropriate to explain for the agglomeration in the sub-nanometer amorphous Ru layers in Ru/C multilayers. The Ru-C phase diagram shows a wide miscible gap, which indicates the preference of phase separation between these two materials and provides an additional driving force for agglomeration. In this paper, we study the evolution of the microstructures and layered structure via in-situ Transmission Electron Microscopy (TEM), and attempt to determine the order of occurence of agglomeration and crystallization in the Ru layers by observing the diffraction patterns.

Effect of Losses in a Layered Structure Containing DPS and DNG Media

PIERS Online ◽  
2008 ◽  
Vol 4 (5) ◽  
pp. 546-550 ◽  
Author(s):  
João R. Canto ◽  
Sérgio A. Matos ◽  
Carlos R. Paiva ◽  
Afonso M. Barbosa
Keyword(s):  
Layered Structure

A striped pattern of snowfall and snow cover

1993 ◽  
Vol 18 ◽  
pp. 27-32
Author(s):  
Yasuaki Nohguchi ◽  
Takashi Ikarashi ◽  
Osamu Abe ◽  
Atsushi Sato
Keyword(s):  
Snow Cover ◽  
Atmospheric Turbulence ◽  
Layered Structure ◽  
Time Variation ◽  
Vertical Wall ◽  
Striped Pattern

A striped pattern can be seen by spraying ink on a vertical wall of a snow pit to observe the layered structure of a snow cover. This pattern is caused by variations of snowfall in time, particularly pauses in snowfall, and its structure is related to a kind of fractal. In this paper, we consider snowfall and snow cover from a viewpoint of fractals and show that the layered structure of snow cover is a record of fractals on atmospheric-turbulence phenomena through the time variation of snowfall.

Study on A-site Cation Doping of CaBi2Nb2O9 with Bismuth Layered Structure

2012 ◽  
Vol 27 (7) ◽  
pp. 726-730 ◽  
Author(s):  
Li-Chao ZONG ◽  
Jiang-Tao ZENG ◽  
Su-Chuan ZHAO ◽  
Wei RUAN ◽  
Guo-Rong LI
Keyword(s):  
Layered Structure ◽  
Cation Doping ◽  
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