Wave propagation can be manipulated at a deep subwavelength scale through the locally resonant metamaterial that possesses unusual effective material properties. Hyperlens due to metamaterial's anomalous anisotropy can lead to superior-resolution imaging. In this paper, a single-phase elastic metamaterial with strongly anisotropic effective mass density has been designed. The proposed metamater...

The Doppler effect refers to the change in frequency of a wave source as a consequence of the relative motion between the source and an observer. Veselago theoretically predicted that materials with negative refractions can induce inverse Doppler effects. With the development of metamaterials, inverse Doppler effects have been extensively investigated. However, the ideal material parameters pre...

A perturbation model for high-frequency sound scattering from an irregular elastic sea bed is considered. The sea bed is assumed homogeneous on the average and two kinds of irregularities are assumed to cause scattering: roughness of the water-sea bed interface and volume inhomogeneities of the sediment mass density and the speeds of compressional and shear waves. The first-order small perturba...

We derive and numerically demonstrate that perfect absorption of elastic waves can be achieved in two types of ultra-thin elastic meta-films: one requires a large value of almost pure imaginary effective mass density and a free space boundary, while the other requires a small value of almost pure imaginary effective modulus and a hard wall boundary. When the pure imaginary density or modulus ex...

Background: The artificial neural networks (ANNs) are useful in solving nonlinear processes, without the need for mathematical models of the parameters. Since the relationship between the CT numbers and material compositions is not linear, ANN can be used for obtaining tissue density and composition.Objective: The aim of this study is to utilize ANN for determination of the composition and mass...

The active mass density in Einstein’s theory of gravitation in the analog of Poisson’s equation in a local inertial system is proportional to ρ+ 3p/c. Here ρ is the density of energy and p its pressure for a perfect fluid. By using exact solutions of Einstein’s field equations in the static case we study whether the pressure term contributes towards the mass.

The distribution of the density of mass in several simple model systems is analyzed. In particular, the relation between the localization of a particle and its mass is studied in detail. The dependence of the function describing mass density distribution on the choice of the reference point and, in this context, the process of emerging the molecular shape as a function of masses of the constitu...

Effective dynamic properties of acoustic metamaterials made of multilayered flexible thin-plates with periodically attached mass-spring resonators are studied. By using the transfer matrix method, the thin-plate acoustic metamaterial under the plane wave incidence is characterized by a homogeneous effective medium with anisotropic mass density. An approximate analytic expression of effective ma...

We use the relationships between galactic H I mass and B-band luminosity determined by Rao & Briggs to recalculate the mass density of neutral gas at the present epoch based on more recent measures of the galaxy luminosity function than were available to those authors. We find Ωgas(z = 0) ≃ 5× 10 −4 in good agreement with the original Rao & Briggs value, suggesting that this quantity is now rea...