Analytical method for evaluating the quality of acoustic fields radiated by a multielement therapeutic array with electronic focus steering

The paper presents an analytical method for calculating and analyzing the quality of 3-D acoustic fields of multielement phased arrays used in noninvasive ultrasound surgical devices. An analytical solution for the far field of each of its elements is used when calculating the array field. This method significantly accelerates calculations while preserving the high accuracy of results as compared to conventional direct numerical integration. Radiation from typical phased arrays is calculated using this approach, and the quality of their dynamic focusing is analyzed. Undesired diffraction effects caused by electronic focus steering are considered: an amplitude decrease in the main maximum and the appearance of grating lobes. The quality of dynamic focusing of the acoustic fields of two practically interesting arrays with a quasi-random element distribution (256 and 1024 elements, respectively), as well as of the regular array consisting of 256 elements is compared. In addition as well, a study is made of how the dimensions of the array elements and their spatial distributions affect the dimensions of the areas in which dynamic focusing is possible without occurrence of strong grating lobes and significant decrease in pressure amplitude at the main focus.

     

The Crystal-Chemical Features of Phases and the Nature of the Coordination Bond in the System [CuxNi(1 – x){N(CH2PO3)3}]Na4 · nH2O (x = 0–1)

Crystallography Reports - The structural features of the phases formed during crystallization of mixed copper and nickel complexes with nitrilotris(methylenephosphonic acid)...     

Creating a Reference Plane Ultrasonic Wave in a Fluid Using a Plane Piezoelectric Transducer with a Large Wave Dimension

Acoustical Physics - The article discusses the possibility of using a plane piezoelectric transducer with a large wave dimension as the source of a reference plane ultrasonic wave, which can be...     

Nonlinear dynamics of a vapor–gas bubble in a superheated region of finite size

A theoretical study of the growth of a spherical vapor bubble in a spherically symmetric superheated region is described. The modeling of bubble dynamics is based on considering the hydrodynamic and thermal processes inside a bubble and the surrounding liquid.     

Calculation of Absorption Intensities of Cr3+ Ion Pair Lines in Ruby

The calculation of relative intensities of the optical absorption lines of the fourth order pair of Cr³⁺ ions in ruby has been performed assuming the electro-dipole character of the transitions.     

Effect of single-walled carbon nanotubes with imide cycles on the synthesis and properties of polycaproamide

The anionic polymerization of ε-caprolactam in the presence of single-walled carbon nanotubes with grafted acyllactam groups or polyimide macromolecules is performed. It is shown that the polymerization of ε-caprolactam slows down with an increase in the filler concentration. The introduction of 0.01 wt % nanotubes with polyimide fragments into polycaproamide leads to a 25% increase in the compressive modulus. In this case, the Izod impact strength is 10 kJ/m², that is, 150% higher than that for an unfilled polycaproamide or polycaproamide containing other types of nanotubes.     

X-ray photoelectron investigation of nanostructures in modified cast irons and steels

A comparative study of industrial samples of classic cast iron, stainless steel, and nanomodified samples was performed. It was shown that the high strength of the obtained materials could be explained by the formation of strong hybridized 3d(Fe) and 3p(Al) bonds, and by the presence of C-C complexes with diamond-like sp ³ hybridization of electrons.     

Determination of the exact solutions to the inhomogeneous burgers equation with the use of the darboux transformation

A method of determining the exact solutions to the Burgers equation on the basis of the Darboux transformation is described. It is shown that a single application of the Darboux transformation to the homogeneous Burgers equation transforms the latter into the inhomogeneous equation describing acoustic wave propagation against transonic flow in the de Laval nozzle. In this case, the contraction ratio of the nozzle is fixed and determined by the viscosity coefficient of the medium. Based on the exact solution of the homogeneous Burgers equation, for the aforementioned problem of the flow in the nozzle, all the possible regular steady-state solutions are presented and the evolution of nonstationary solutions is investigated. The algorithm of a multiple Darboux transformation, which allows an increase in the strength of inhomogeneity, i.e., in the contraction ratio of the nozzle, is determined. This approach leads to a discrete set of possible contraction ratios at which exact solutions can be obtained. The Crum’s theorem is used to derive a formula that allows determination of the exact solutions to the inhomogeneous Burgers equation from the solutions to the homogeneous heat transfer equation. It is noted that, in fact, the proposed algorithm of the multiple Darboux transformation makes it possible to decrease the viscosity coefficient of the medium in a discrete way.     

Nanobiocomposites of Pharmacophoric Iron and Bismuth Oxides with Arabinogalactan Matrix

Water-soluble nanocomposites with narrow distribution of nanoparticles of pharmacophore bismuth and iron oxides have been obtained. The biopolymer matrix of the arabinogalactan polysaccharide has exhibited strong stabilizing properties with respect to transition metal oxides. The size of the spherical metal oxide nanoparticles has been found of 5–7 nm as per transmission electron microscopy. The exclusion liquid chromatography data have revealed that the change in the molecular mass parameters of arabinogalactan is due to the combined processes of self-assembly of nanocomposites and alkaline decomposition.