Wave Manipulation of Two-Dimensional Periodic Lattice by Parametric Excitation

2019 ◽  
Vol 87 (1) ◽  
Author(s):  
Xiao-Dong Yang ◽  
Qing-Dian Cui ◽  
Wei Zhang
Keyword(s):  
Parametric Excitation ◽  
Elastic Waves ◽  
High Frequency ◽  
Low Frequency ◽  
Waveguide Structure ◽  
Phononic Crystals ◽  
Periodic Lattice ◽  
Two Dimensional ◽  
Time Dynamic ◽  
Mechanical Waves

Abstract Phononic crystals composed of delicately designed periodic units are used to control spatial and spectral properties of acoustic or elastic waves. The ability to manipulate transmitting waves in a real-time dynamic manner provides a new concept in programable phononic crystals and metamaterials. In this study, the mechanical waves and bandgaps in a two-dimensional spring-mass array loaded by high-frequency parametric excitation have been investigated by both analytical and numerical methods. It is found that the high-frequency parametric excitation provides an equivalent additional stiffness which leads to low-frequency bandgaps. By tuning the parametric excitation, the versatility of such a dynamic modulating technique has been presented. The waveguide structure has also been designed and studied by non-uniformly distributed parametric excitations.

Despeckling of Sar Images Using Shrinkage of Two-Dimensional Discrete Orthonormal S-Transform

2020 ◽  
pp. 2150023
Author(s):  
Priya R. Kamath ◽  
Kedarnath Senapati ◽  
P. Jidesh
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Relevant Information ◽  
Detection Algorithm ◽  
Two Dimensional ◽  
Sar Images ◽  
S Transform ◽  
Processing Step ◽  
Frequency Components ◽  
Shock Filter

Speckles are inherent to SAR. They hide and undermine several relevant information contained in the SAR images. In this paper, a despeckling algorithm using the shrinkage of two-dimensional discrete orthonormal S-transform (2D-DOST) coefficients in the transform domain along with shock filter is proposed. Also, an attempt has been made as a post-processing step to preserve the edges and other details while removing the speckle. The proposed strategy involves decomposing the SAR image into low and high-frequency components and processing them separately. A shock filter is used to smooth out the small variations in low-frequency components, and the high-frequency components are treated with a shrinkage of 2D-DOST coefficients. The edges, for enhancement, are detected using a ratio-based edge detection algorithm. The proposed method is tested, verified, and compared with some well-known models on C-band and X-band SAR images. A detailed experimental analysis is illustrated.

Low frequency phononic band structures in two-dimensional arc-shaped phononic crystals

2012 ◽  
Vol 376 (33) ◽  
pp. 2256-2263 ◽  
Author(s):  
Zhenlong Xu ◽  
Fugen Wu ◽  
Zhongning Guo
Keyword(s):  
Low Frequency ◽  
Phononic Crystals ◽  
Two Dimensional ◽  
Band Structures

Localisation of elastic waves in two-dimensional randomly disordered solid phononic crystals

2010 ◽  
Vol 20 (1) ◽  
pp. 104-121 ◽  
Author(s):  
A-Li Chen ◽  
Yue-Sheng Wang ◽  
Jian-Bao Li ◽  
Chuanzeng Zhang
Keyword(s):  
Elastic Waves ◽  
Phononic Crystals ◽  
Two Dimensional

Propagation of elastic waves in two-dimensional phononic crystals composed of viscoelastic materials

2017 ◽  
Vol 56 (3) ◽  
pp. 034101 ◽  
Author(s):  
Yukihiro Tanaka ◽  
Shunsuke Tomioka ◽  
Yukito Shimomura ◽  
Norihiko Nishiguchi
Keyword(s):  
Elastic Waves ◽  
Phononic Crystals ◽  
Two Dimensional ◽  
Viscoelastic Materials ◽  
Propagation Of Elastic Waves

scholarly journals Model involving gene inactivation in the generation of autosomal recessive mutants in mammalian cells in culture.

1982 ◽  
Vol 2 (9) ◽  
pp. 1126-1133 ◽  
Author(s):  
A E Simon ◽  
M W Taylor ◽  
W E Bradley ◽  
L H Thompson
Keyword(s):  
Chinese Hamster Ovary ◽  
High Frequency ◽  
Mammalian Cells ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Low Frequency ◽  
Two Dimensional ◽  
Wild Type ◽  
Proposed Model ◽  
Class 1

We present evidence for a two-step model for expression of the recessive phenotype at the diploid adenine phosphoribosyl transferase (aprt) locus in Chinese hamster ovary cells. This model proposes a high-frequency event leading to allelic inactivation and a low-frequency event leading to a structural alteration of the APRT protein. Either event can occur first, resulting in two types of heterozygous cells. The proposed model is based on analysis of Chinese hamster ovary presumptive aprt heterozygotes and APRT- mutants, derived by two different laboratories. The major class of heterozygotes (class 1) had approximately 50% parental APRT activity, 50% immunologically precipitable APRT protein, and only wild-type enzyme as based on two-dimensional gel electrophoresis and thermal inactivation studies. We propose that one allele at the aprt locus has been inactivated in these heterozygotes. APRT- mutants derived from any single class 1 heterozygote arose at a low frequency and contained either no immunologically detectable APRT protein or an APRT enzyme which was, in most cases, demonstrably altered. The second class of heterozygotes, consisting of two independent isolates, gave rise to APRT- cells at a high frequency (10(-3) to 10(-5). These heterozygous cell lines had 50% of parental APRT activity and only wild-type spot, or wild-type and an electrophoretic variant spot, on two-dimensional gels. These aprt heterozygotes appear to have arisen by mutation at one allele. APRT- mutants derived from either heterozygote of this class had all lost the wild-type activity, consistent with the proposed model.

Elastic Metamaterials With Low-Frequency Passbands Based on Lattice System With On-Site Potential

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
Yongquan Liu ◽  
Xiaohui Shen ◽  
Xianyue Su ◽  
C. T. Sun
Keyword(s):  
Elastic Waves ◽  
Present Method ◽  
Wave Attenuation ◽  
Low Frequency ◽  
Lattice System ◽  
Two Dimensional ◽  
High Frequencies ◽  
Elastic Metamaterials

An elastic metamaterial with a low-frequency passband is proposed by imitating a lattice system with linear on-site potential. It is shown that waves can only propagate in the tunable passband. Then, two kinds of elastic metamaterials with double passbands are designed. Great wave attenuation performance can be obtained at frequencies between the two passbands for locally resonant type metamaterials, and at both low and high frequencies for the diatomic type metamaterials. Finally, the strategy to design two-dimensional (2D) metamaterials is demonstrated. The present method can be used to design new types of small-size waveguides, filters, and other devices for elastic waves.

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