Narrow Results

We examine the three-dimensional problem associated with a spheroidal dielectric compressible liquid inclusion perfectly bonded to an infinite transversely isotropic piezoelectric matrix subjected to a uniform axisymmetric electromechanical loading at infinity. Our solution method is based on the general solution developed by [L. Kogan, C. Y. Hui and V. Molkov. Stress and induction field of a spheroidal inclusion or a penny-shaped crack in a transversely isotropic piezoelectric material. International Journal of Solids and Structures33(19), pp. 2719–2737, 1996] describing the electroelastic field in a transversely isotropic piezoelectric solid. Specifically, the original boundary value problem is reduced to a set of four coupled linear algebraic equations. The internal uniform hydrostatic stress field within the liquid inclusion and the electroelastic field of displacements, electric potential, stresses and electric displacements in the piezoelectric matrix are then completely determined via the solution of this set of linear algebraic equations. A three-dimensional neutral liquid inclusion of arbitrary shape that does not disturb the prescribed uniform hydrostatic stresses and electric displacements in a generally anisotropic piezoelectric matrix is achieved.

An elementary cellular automaton (ECA) is a one-dimensional, synchronous, binary automaton, where each cell update depends on its own state and states of its two closest neighbors. We attempt to uncover correlations between the following measures of ECA behavior: compressibility, sensitivity and diversity. The compressibility of ECA configurations is calculated using the Lempel–Ziv (LZ) compression algorithm LZ78. The sensitivity of ECA rules to initial conditions and perturbations is evaluated using Derrida coefficients. The generative morphological diversity shows how many different neighborhood states are produced from a single nonquiescent cell. We found no significant correlation between sensitivity and compressibility. There is a substantial correlation between generative diversity and compressibility. Using sensitivity, compressibility and diversity, we uncover and characterize novel groupings of rules.

Two-dimensional (2D) electron systems in the presence of disorder are of interest in connection with the observed metal-insulator transition in such systems. We use density functional theory in its local-spin density approximation (LSDA) to calculate the ground-state energy of a 2D electron system in the presence of remote charged impurities which up on averaging provides disorder. The inverse compressibility calculated from the ground-state energy exhibits a minimum at a critical density controlled by the disorder strength. Our findings are in agreement with experimental results.

Correlations in quantum fluids such as liquid ³He continue to be of high interest to scientists. Based on this prospect, the present work is devoted to study the effects of spin–spin correlation function on the thermodynamic properties of polarized liquid ³He such as pressure, velocity of sound, adiabatic index and adiabatic compressibility along different isentropic paths, using the Lennard–Jones potential and employing the variational approach based on cluster expansion of the energy functional. The inclusion of this correlation improves our previous calculations and leads to good agreements with experimental results.

The quantum second virial coefficient B${}_q$ of ³He${}^{\uparrow }$ gas is determined in the temperature range 0.001–4 K from the Beth–Uhlenbeck formula. The corresponding phase shifts are calculated from the Lippmann–Schwinger equation using a highly-accurate matrix-inversion technique. A positive B${}_q$ corresponds to an overall repulsive interaction; whereas a negative B${}_q$ represents an overall attractive interaction. It is found that in the low-energy limit, B${}_q$ tends to increase with increasing spin polarization. The compressibility Z is evaluated as another measure of nonideality of the system. Z becomes most significant at low temperatures and increases with polarization. From the pressure–temperature (P–T) behavior of ³He${}^{\uparrow }$ at low T, it is deduced that P decreases with increasing T below 8 mK.

Ice accretion on aircraft is studied by a numerical method. By solving governing equations, the flow field is obtained for analyzing the icing zone and calculating the ice quantity on different parts. Influence of the fluid viscosity and compressibility on icing characters is extensively studied. And it can be found that the results agree well with those calculated by LEWICE program. This achievement could be helpful to further research on ice accretion.

A size-dependent gradient method is used to study the Mie scattering visualization of the compressible turbulent mixing layers at two convective Mach numbers M_c = 0.107 and 0.474 in order to reveal multi-scale structures. Coherent vortices and inclined wavy structures are clearly visualized by applying the method. Similarity between the grey-level and the velocity fluctuations is discovered with the spectral analysis. These results suggest a way to capture turbulent structures from scalar fields.

Recently first principles microscopic calculations, using the generalized gradient approximation, appeared for the solid mixed system AgCl_xBr_1-x at various compositions. Here, we suggest a model that can estimate the compressibility of the mixed crystals in terms of the compressibilities of the end members alone. This model makes use of a single parameter, i.e. the compressibility of a defect volume, when considering the volume variation produced by the addition of a "foreign molecule" to a host crystal as a defect volume.

We study the effects of isovector-scalar ($\delta$)-meson on neutron and hyperon stars. Influence of $\delta$-meson on both static and rotating stars is discussed. The $\delta$-meson in a neutron star consisting of protons, neutrons and electrons, makes the equations of states (EOS) stiffer at higher density, and consequently increases the maximum mass of the star. But induction of $\delta$-meson in the hyperon star decreases the maximum mass. This is due to the early evolution of hyperons in presence of $\delta$-meson.

This paper is devoted to mathematical modeling of anisotropic hyperelastic thick cylindrical shells like arteries by taking into account the volume compressibility and through-the-thickness deformation. To describe the hyperelastic behavior of this kind of shells and extract their constitutive relations, the modified anisotropic (MA) model is employed, which is able to characterize compressible behavior of hyperelastic materials like soft tissues. By considering the arterial segment as a thick cylindrical shell, the higher order thickness deformation shell theory together with nonlinear Green’s strains are exploited to express its deformations and capture the thickness stretching effect. The shell is then discretized via Lagrange equations of motion to achieve the responses of the arterial wall. Numerical results are given in two sections. First, the presented formulation is validated by conducting a comparative study on a single-layer compressible pressurized shell. Close agreement between the outcomes of the developed model with those provided by finite element (FE) simulation signifies the necessity of incorporating thickness deformation in the higher order shell theory. In the next step, by considering the artery as a two-layer cylindrical shell comprising the media (the middle layer of the artery) and the adventitia (the outer layer), mechanical responses of an arterial wall subjected to an internal pressure are appraised through a number of parametric studies.

The design of a new digital radio receiver for radio astronomical observations in outer space is challenged with energy and bandwidth constraints. This paper proposes a new solution to reduce the number of samples acquired under the Shannon–Nyquist limit while retaining the relevant information of the signal. For this, it proposes to exploit the sparsity of the signal by using a compressive sampling process (also called Compressed Sensing (CS)) at the Analog-to-Digital Converter (ADC) to reduce the amount of data acquired and the energy consumption. As an example of an astrophysical signal, we have analyzed a real Jovian signal within a bandwidth of 40MHz. We have demonstrated that its best sparsity is in the frequency domain with a sparsity level of at least 10% and we have chosen, through a literature review, the Non-Uniform Sampler (NUS) as the receiver architecture. A method for evaluating the reconstruction of the Jovian signal is implemented to assess the impact of CS compression on the relevant information and to calibrate the detection threshold. Through extensive numerical simulations, and by using Orthogonal Matching Pursuit (OMP) as the reconstruction algorithm, we have shown that the Jovian signal could be sensed by taking only 20% of samples at random, while still recovering the relevant information.

Two-dimensional (2D) electron systems in the presence of disorder are of interest in connection with the observed metal-insulator transition in such systems. We use density functional theory in its local-spin density approximation (LSDA) to calculate the ground-state energy of a 2D electron system in the presence of remote charged impurities which up on averaging provides disorder. The inverse compressibility calculated from the ground-state energy exhibits a minimum at a critical density controlled by the disorder strength. Our findings are in agreement with experimental results.