Scattering of high-frequency waves by surfaces in continuous media with allowance for rereflections

This study is devoted to the development of the ray theory of diffraction in application to arbitrary (nonconvex) smooth obstacles in the scalar case. A three-dimensional problem is considered. An asymptotic method of estimating the diffraction integrals is described. The method is based on the multidimensional stationary phase approach. The diffraction integrals are obtained on the basis of the generalization of the Kirchhoff physical theory of diffraction. Explicit expressions are derived for the pressure in the reflected wave in the cases of its single and double reflections.     

Effect of internal waves on the intensity and interference structure of the sound field in a shelf zone

Experimental data obtained by studying the effect of internal waves with known space-time parameters on the propagation of a 240-Hz tone signal and on the space-time interference structure of the sound field generated by a noiselike sound source are presented.     

Structure and electronic properties of hydrogenated amorphous GaP

Hydrogenated amorphous GaP films have been prepared by reactive rf sputtering. Infrared spectroscopy, optical transmission and reflection, photothermal deflection spectroscopy and dc conductivity have been studied to investigate the local bonding configurations, the optical absorption edges and the temperature dependence of the conductivity as a function of hydrogen content. The results are discussed and compared with the effects of hydrogenation on amorphous Si.     

Mathematical Simulation of the Synthesis of cis-1,4-Polybutadiene on a Cobalt-Containing Catalyst in the Presence of Ethylene

Based on an analysis of experimental results and published data, the main elementary steps of the anionic coordination polymerization of butadiene rubber on a cobalt-containing catalyst in the presence of ethylene were found, and a mathematical model of the periodic process at an optimum water content was developed. The molecular-weight characteristics of the process depending on ethylene concentration were studied with the use of this model.     

A Study of Drop Size Distribution in Multistage Bubble Extractor

Results obtained in determining experimentally the mean volume-surface drop diameter of the dispersed phase in a multistage bubble extractor are presented.     

Kinetics of a photoinduced NH tautomerism of free-base porphyrins in crystalline matrices at low temperatures: Computer simulations and experiment

Photoinduced NH tautomerism, along with the reaction pathways of phototautomerization in tetrabenzoporphin and porphin free bases in n-octane polycrystalline matrices at 77 K, is studied by simulation of kinetic processes and their experimental observation. The simulation of the processes is performed by the numerical solution of the system of kinetic equations describing the populations of electronic levels and transitions between them. Kinetic dependences are obtained by measuring the perturbation of stationary fluorescence of one component of the 0-0 doublet origin upon pulsed selective photoexcitation of the other component. For two tautomeric forms related by the reversibility of the photochemical reaction, under the assumption of synchronism of the NH rearrangement, (i) analytical solutions governing the reaction rate are found, (ii) a method of measuring the rate constants of the proton rearrangement is suggested and the constants themselves are estimated, and (iii) direct evidence of the participation of T ₁ levels in the photochemical reaction is obtained. With the aid of numerical simulations, the specific features of kinetic manifestation of an asynchronous mechanism of the photoinduced NH rearrangement are studied.     

Search for the emission of π<Superscript>0</Superscript> mesons from the neutron-induced fission of <Superscript>235</Superscript>U nuclei

A nuclear-reactor experiment on the search for the emission of neutral pions from the neutron-induced fission of ²³⁵U nuclei has been carried out. To this end, an experimental setup for searching for the emission of π⁰ mesons with high sensitivity to this process has been designed and produced. This setup consisted of two Cherenkov total-absorption spectrometers for the detection and measurements of the energy of two gamma-ray photons from π ⁰-meson decay. The spectrometers were placed at the exits of two coaxial horizontal experimental channels. To protect the detectors from low-energy β and γ rays and neutron fluxes, 3.5-m-long water filters were situated in the channels. To reject the cosmic background, large-area scintillation counters operating in the anticoincidence mode were placed over each spectrometer. The energy and time resolution of the spectrometers, as well as the efficiency of detecting charged particles by scintillation counters, were tested on the secondary electron beam of the Tomsk electron synchrotron Sirius. Runs of measurements of the effect on the operating reactor (duration of 805 h) were alternated with runs of measurements of background on the stopped reactor (duration of 403 h). Statistical processing of the experimental results yields an upper limit of ≤5.3×10 ^?12 with a 90% confidence level for the probability of the emission of neutral pions from the neutron-induced fission of ²³⁵U nuclei. This result and results of other works carried out with sources of spontaneously fissioning ²⁵²Cf nuclei show that the probabilities of the emission of π⁰ mesons from spontaneous fission and fission induced by fission-spectrum neutrons are equal to each other.     

A two dimensional, experimental study on the evolution of the detachment and its time-behavior in filled rubber

Summary The detachment of a rubber matrix from a rigid inclusion under monotonic loading and at subsequent relaxation is investigated within two dimensional analysis. Examined are stress–strain experimental data acquired with the help of a test bed equipped with a digital image-acquisition device. The influence of the interfacial bonding strength and the particle size on the detachment process is analyzed. The influence of the interfacial bonding strength is visible in the stress–strain diagram of loading and in the recorded images. The relaxation test reveals no influence of the bonding strength on the stress-relaxation. However, the image analysis indicates a secondary transient creep of the contour of detachment, which depends on the interfacial bonding.     

On the regime of trapping of optical fiber solitons by a control signal

A scheme of trapping of temporal solitons by a moving grating induced in an optical fiber by external radiation is proposed. Prospects for using the scheme to increase the capacity and the range of data transmission with the help of dissipative solitons are discussed.