Ways to improving the thermal stability of organosilicon elastomeric materials

Samples of silicone elastomeric materials based on linear ladder block copolymers containing linear polydimethylsiloxane and ladder phenylsilsesquioxane molecular units have been obtained and investigated. It has been shown that the use of such block copolymers of the brands Lestosil N and Lestosil SM improves the heat resistance of the obtained vulcanizates up to 350°C for a long time.     

Comparison of flows induced by a dielectric barrier discharge and a sliding discharge

Two types of electric discharges to be used for the purpose of air flow control are compared. The parameters measured in experiments are the electric characteristics of the discharges and the velocity of flows generated by them. The ionic wind velocity in the sliding discharge is demonstrated to be smaller than in the dielectric barrier discharge. The volume forces acting from the discharge on air and the efficiency of the electro-gas-dynamic action are estimated. The presence of an additional electrode in the case of the sliding discharge is found to affect the distribution of the spatial charge and change the forces, leaving the electric characteristics unchanged.     

Effect of the rise time of the remagnetizing pulse on the nanosecond remagnetization of permalloy films

A study was made of the effect of the rise time of the remagnetizing pulse on the nanosecond-remagnetization signals of permalloy films, on the average-magnetization trajectory, and on the effective damping parameter. These effects intensify with increasing coercive force of the films.Translated from Izvestiya Vysshikh Uchenbykh Zavedenii Fizika, No. 2, pp. 7–10, February, 1971.     

Solvent Regeneration in Direct Synthesis of Alkoxysilanes

A procedure was developed for regeneration of Termolan, solvent used in synthesis of alkoxysilanes, involving its treatment with ethanol to remove alkoxysilanes.     

Manifestation of directional dispersion of overdamped optical phonons in Raman spectra

This study is devoted to the analysis of the features of the manifestation of the directional dispersion of strongly damped (overdamped) optical phonons in Raman spectra. The results of the experimental study of the directional dispersion of the overdamped soft mode of symmetry B ₂(z) of the KDP crystal (KH₂PO₄) are presented.     

On the determination of the position of laminar-turbulent transition in boundary layer by optical methods

As a rule, aerodynamic studies at hypersonic flow velocities are carried out in short-duration wind-tunnel facilities. For such facilities, optical diagnostic methods are most preferable. In the present study, we give for the first time a comparison of two methods for determining the end of laminar-turbulent transition: from the distribution of heat fluxes and from schlieren visualization data for the boundary-layer flow. Parametric data on the position of the transition are obtained. These data can be used in the future as reference ones while calibrating semi-empirical calculation models for the transition.     

An experimental study of the natural noise in the Transit-M hypersonic wind tunnel

Tests were performed at Mach number M = 6. Observations of flow pulsations were performed with the help of high-frequency measurements of pressure and heat fluxes and with the help of hot-wire anemometry. Measurements were carried out in a broad range of Re₁ numbers at various orientations and locations of sensors with respect to the nozzle exit plane. It is shown that the Transit-M noise varies weakly over the longitudinal coordinate, whereas on moving along the radial coordinate, some increase of the fluctuation level is observed due to approaching the mixing layer. Also, the distribution of axial asymmetry of the noise level was obtained.     

Turbulization of the wake behind a single roughness element on a blunted body at a hypersonic Mach number

The influence of a cylinder-shaped single roughness element on the laminar–turbulent transition in the presence of an entropy layer is experimentally studied. The experiments are performed on a blunted cone model at the Mach number M = 5. The roughness element is located on the blunted tip of the model. Information about the mean and fluctuating parameters of the boundary layer in the wake behind the roughness element is obtained by using hot-wire anemometry. It is shown that flow turbulization behind the roughness elements occurs at the local Reynolds number calculated on the basis of the roughness element height and equal to 400–500. It is found that the presence of the roughness element exerts a significant effect on the unsteady characteristics of the boundary layer if the roughness element height is smaller than the effective value.     

New thermally conductive silicone adhesive sealants

Single-component silicone adhesive sealants of the Elasil range of the 137-182М, 137-182М1, 137-182М2, and 137-182М3 brands developed at the Scientific Research Institute of Chemistry and Technology of Organoelement Compounds are presented. It is demonstrated by the results of thermophysical tests that their coefficient of thermal conductivity is more than 1.5-fold higher than the coefficient of thermal conductivity of an Elasil 137-182 commercial single-component silicone adhesive sealant and they can be used in radioelectronic equipment to abstract heat generated from heat-loaded elements.