The formulation of the problem of surface control of an electroactive unidirectional multicomponent elastic wave propagation in an infinite piezoelectric waveguide over a finite time interval is ...discussed. Based on the conditions for conjugation of electromechanical fields on the surface of piezoelectric media, as well as on the nature of possible surface electromechanical effects, a variety of surface dynamic effects is considered through the components of the elastic displacement vector, the mechanical stress tensor, the tangential component of the electric field strength and the normal component of the electric field displacement. The possibility of setting the control problem in the case of three-component electroacoustic waves depending on the anisotropy of the piezoelectric material of the waveguide is studied. The anisotropy of a piezoelectric medium leads to the formulation of an initial-boundary mathematical problem for controlling the motion of a multicomponent system. The variety of surface actions leads to the formulation of heterogeneous initial-boundary mathematical problems with surface actions of the first kind, with surface actions of the second kind, as well as for the case of mixed surface actions. An invariant record of heterogeneous initial-boundary mathematical problems is proposed in the form of a system of inhomogeneous quasi-static electro-elasticity equations, with homogeneous boundary conditions and inhomogeneous conditions of the initial and final states
.
The possibility of formulating problems of controlling electroacoustic transverse waves propagating in a piezoelectric half-space via nonacoustic influence on its surface is investigated. The ...presence of a conducting surface near the mechanically free surface of a piezoelectric half-space changes the character of the near-surface localization of the propagating electroacoustic wave in it. Based on this, the formulation of the problem of controlling the wave localization process is proposed. It is shown that an unsteady electric potential at an electric shield or the nonstationarity of the gap width between these surfaces lead to a nonacoustic effect on the piezoelectric half-space. In problems of controlling the near-surface wave-energy localization, nonacoustic effects on the surface of the piezoelectric half-space are used as a control function.
Abstract
In this work, the effect of TOEPyP4 porphyrins on DNA damage induced by X-ray beams was investigated. The influence of X-ray radiation with different doses on DNA isolated from the calf ...thymus, as well as DNA/TOEPyP4 complexes, was investigated. To study the influence of the presence of porphyrins on radiation induced DNA damages with different relative concentrations of complexes were investigated (r = 0.01; 0.04, where r = C
porf.
/C
DNA
). Then an attempt was made to reveal the possible potentiating effects of porphyrins on DNA damage depending on the concentration of porphyrins and the radiation dose. The studies were carried out by the spectroscopy melting method in 10
-3
M NaCl buffer solution, pH 7.2. From obtaining dates, the dependence of the protective or radiation-enhancing properties of porphyrins on the relative concentrations - irradiation dose combination is evident.
Studies of the cross section of gamma-neutron reactions on the
Nb nucleus were carried out on the bremsstrahlung of the linear electron accelerator LUE-75 which is located at the A. Alikhanyan ...National Science Laboratory (Yerevan Physics Institute). The experiment was done at 30 and 40 MeV bremsstrahlung end-point energies. The reaction cross sections for
Nb
Nb reactions were measured by the activation method with the spectrometric analysis using the High Purity Germanium detector (HPGe). The values of cross sections for different energies of photon beam were determined using the TALYS 1.95 and EMPIRE 3.2 nuclear codes. The energy distribution of photon spectra was performed using the GEANT4 package. The obtained experimental and theoretical results are compared with the available experimental data of other authors. Good agreement was observed between the theoretical and experimental data. The data on the reaction cross section for
Nb
Nb were obtained for the first time.
Abstract
Investigating the reflection and refraction of electroelastic waves at a plane interface without acoustic contact between two piezoelectric half-spaces of different textures, it was found ...that: (i)As a result of the incidence of a two-component electroelastic shear wave on the interface between the media, the same wave is reflected into the first half-space, and a three-component electroelastic plane strain wave is refracted into the second half-space. In the utmost cases, in layered inhomogeneous waveguide, a wave hybrid of electroacoustic waves is formed. This makes it possible to transmit along the boundary of non-acoustic contact of media a hybrid of electroacoustic surface waves of the Gulyaev-Bluestein type and Rayleigh type localized near this boundary. (ii)As a result of the incidence of a two-component electroelastic plane strain wave on the interface between the media, the same wave is reflected into the first half-space, and a three-component electroelastic shear wave is refracted into the second half-space. This also makes it possible to organize a hybrid of electroacoustic waves of elastic shear and plane deformation of the type of periodic electroelastic Floquet waves in a periodically transversely inhomogeneous piezoelectric composite. The conditions for the possible formation of the hybrid and the characteristics of their propagation in the layered composites of piezoelectrics of the hexagonal symmetry class 6
mm
and
6
¯
m
2 are discussed.
To identify the role of the gamma radiation from radon progenies in long-lasting thunderstorm ground enhancement (TGE) flux, the differential energy spectrum is measured with various spectrometers, ...including precise spectrometer of ORTEC firm built with 3"×3" inches sodium iodide NaI(Tl) crystal; full width at half maximum (FWHM) ∼7.7% at 0.6 MeV. The measurements demonstrate that radon progeny radiation significantly contributes to the count rate enhancements measured in the winter of 2018–2019 in the energy range below 3 MeV. However, performed Monte Carlo simulations and observation of long-lasting TGEs with plastic scintillators of various thicknesses and energy thresholds show that TGEs originate in the intracloud electric fields. Radon progenies (mostly Bi214 spectral lines) contribute to count rate in the low-energy domain.
PDF
